As filed with the Securities and Exchange Commission on June 4, 2018.

Registration No. 333-          

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT

Under

The Securities Act of 1933

ALTAIR ENGINEERING INC.

(Exact name of registrant as specified in its charter)

1820 E. Big Beaver Road

Troy, Michigan 48083

(248) 614-2400

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

James R. Scapa

Chief Executive Officer

Altair Engineering Inc.

1820 E. Big Beaver Road, Troy, Michigan 48083

(248) 614-2400

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after the effective date of this Registration Statement.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933 check the following box:  ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.  ☐

CALCULATION OF REGISTRATION FEE

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with section 8(a) of the Securities Act of 1933 or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said section 8(a), may determine.

The information in this prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is declared effective. This prospectus is not an offer to sell these securities or a solicitation of an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to completion, dated June 4, 2018

Prospectus

5,600,000 Shares

Class A common stock

$         per share

We are offering 3,292,580 shares of our Class A common stock and the selling stockholders identified in this prospectus are offering 2,307,420 shares of our Class A common stock. We will not receive any of the proceeds from the shares of Class A common stock sold by the selling stockholders.

Our Class A common stock is listed on the NASDAQ Global Select Market under the symbol “ALTR.” On May 31, 2018, the last reported sale price of our Class A common stock as reported on the NASDAQ Global Select Market was $35.19 per share.

We have two classes of common stock, Class A common stock and Class B common stock. The rights of the holders of Class A common stock and Class B common stock are identical, except with respect to voting and conversion rights. Each share of Class A common stock is entitled to one vote per share. Each share of Class B common stock is entitled to ten votes per share and is convertible into one share of Class A common stock. The holders of our outstanding Class B common stock will hold approximately 91% of the voting power of our outstanding capital stock following this offering, with our directors, executive officers and current beneficial owners of 5% or more and their affiliates holding approximately 92% of the voting power.

We are an “emerging growth company” as defined under federal securities laws. We anticipate that following the completion of this offering, our chairman and chief executive officer will continue to control a majority of the combined voting power of our common stock. While under NASDAQ rules we may be deemed a “controlled company,” we do not intend to take advantage of the corporate governance exemptions afforded to a “controlled company” under NASDAQ rules.

Investing in our Class A common stock involves a high degree of risk. Please see the section titled “Risk factors” starting on page 18 to read about risks you should consider carefully before buying shares of our Class A common stock.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

We have granted the underwriters a 30-day option to purchase up to an additional 840,000 shares of Class A common stock at the public offering price, less the underwriting discount.

The underwriters expect to deliver the shares on or about                 , 2018.

The date of this prospectus is                 , 2018

Table of contents

Neither we, the selling stockholders, nor the underwriters have authorized anyone to provide any information or to make any representations other than those contained or incorporated by reference in this prospectus or in any free writing prospectuses we have prepared. We and the selling stockholders take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We and the selling stockholders are offering to sell, and seeking offers to buy, shares of our common stock only in jurisdictions where offers and sales are permitted. The information contained or incorporated by reference in this prospectus is accurate only as of the date of this prospectus or the date of the applicable document incorporated by reference, regardless of the time of delivery of this prospectus or any sale of shares of our common stock. Our business, financial condition, results of operations, and prospects may have changed since that date.

For investors outside the United States: Neither we, the selling stockholders, nor the underwriters have done anything that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of the shares of our common stock and the distribution of this prospectus outside of the United States.

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Risk factors

Investing in our Class A common stock involves a high degree of risk. You should carefully consider the risks and uncertainties described below, as well as those set forth under the heading “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2017, as updated by our Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, which are incorporated by reference in this prospectus. Our business, operating results, financial condition or prospects could be materially and adversely affected by any of these risks and uncertainties. In that case, the trading price of our Class A common stock could decline and you might lose all or part of your investment. In addition, the risks and uncertainties discussed below and in the documents incorporated by reference are not the only ones we face. Our business, operating results, financial condition or prospects could also be harmed by risks and uncertainties not currently known to us or that we currently do not believe are material, and these risks and uncertainties could result in a complete loss of your investment. In assessing the risks and uncertainties described below, you should also refer to the other information contained in this prospectus (as supplemented or amended) and the documents incorporated by reference in this prospectus, including our consolidated financial statements and the related notes thereto, before making a decision to invest in our Class A common stock.

Risks related to this offering and ownership of our Class A common stock

Our management has broad discretion in the use of the net proceeds from this offering, and our use of the net proceeds may not enhance our operating results or the price of our Class A common stock.

We intend to use the net proceeds to us from this offering for general corporate purposes, including working capital, sales and marketing activities, general and administrative matters, real estate development, including developing and building an addition adjacent to our corporate headquarters facilities, and capital expenditures. We may also use a portion of the net proceeds for the acquisition of, or investment in, technologies, solutions or businesses that complement our business. While we do not have agreements or binding commitments for any specific acquisitions at this time, we continually evaluate potential acquisition candidates to enhance our product offerings. Accordingly, our management will have considerable discretion over the specific use of the net proceeds that we receive in this offering and might not be able to obtain a significant return, if any, on investment of these net proceeds. You will not have the opportunity as part of your investment decision to assess whether the net proceeds are being used appropriately. Investors in this offering will need to rely upon the judgment of our management with respect to the use of proceeds. Until the net proceeds are used, they may be placed in investments that do not produce significant income, may be held in demand deposit accounts, or in investments intended to be highly liquid that may nevertheless lose value. If we do not use the net proceeds that we receive in this offering effectively, our business and prospects could be harmed, and the market price of our Class A common stock could decline.

As a new investor, you will experience immediate and substantial dilution in the book value of the shares that you purchase in this offering.

The assumed public offering price is substantially higher than the net tangible book value per share of our Class A common stock immediately following this offering based on the total value of our tangible assets less our total liabilities. Therefore, if you purchase shares of our Class A common stock in this offering, at the assumed public offering price of $35.19 per share, the last reported sale price of our Class A common stock on the NASDAQ Global Select Market on May 31, 2018, you will experience immediate dilution of $33.84 per share, the difference between the price per share you pay for our Class A common stock and our net tangible book value per share as of March 31, 2018, after giving effect to the issuance of shares of our common stock in this offering. See the section titled “Dilution” for more information.

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Our Class A common stock has only recently become publicly traded, and the market price of our Class A common stock may be volatile.

The market price of our Class A common stock may fluctuate substantially depending on a number of factors, many of which are beyond our control and may not be related to our operating performance. These fluctuations could cause you to lose all or part of your investment in our Class A common stock, since you might not be able to sell your shares at or above the price you paid for our Class A common stock. Factors that could cause fluctuations in the market price of our Class A common stock include the following:

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In addition, the stock market in general, and the market for technology companies in particular, have experienced extreme price and volume fluctuations that have often been unrelated or disproportionate to the operating performance of those companies. Broad market and industry factors may affect the market price of our Class A common stock, regardless of our actual operating performance. In the past, following periods of volatility in the overall market and the market prices of a particular company’s securities, securities class action litigation has often been instituted against that company. We may become the target of this type of litigation in the future. Securities litigation, if instituted against us, could result in substantial costs and divert our management’s attention and resources from our business.

Sales of substantial amounts of our Class A common stock could cause the market price of our common stock to decline and may dilute your voting power and your ownership interest in us.

Sales of a substantial number of shares of our Class A common stock after this offering, particularly sales by our directors, executive officers and significant stockholders could adversely affect the market price of our Class A common stock and may make it more difficult to sell Class A common stock at a time and price that you deem appropriate. Based on the total number of outstanding shares of our common stock as of March 31, 2018, upon completion of this offering, we will have an aggregate of 32,582,012 shares of Class A common stock and 34,832,256 shares of Class B common stock outstanding, assuming no exercise of our outstanding stock options or settlement of restricted stock units after March 31, 2018 and assuming the underwriters do not exercise their option to purchase additional shares.

All of the shares of Class A common stock sold in this offering will be freely tradable without restrictions or further registration under the Securities Act of 1933, as amended, or the Securities Act, except for any shares held by our affiliates as defined in Rule 144 under the Securities Act. Shares held by directors, executive officers and other affiliates will be subject to volume limitations under Rule 144 under the Securities Act and various vesting agreements.

In addition, as of March 31, 2018, there were 8,877,036 shares of Class A common stock subject to outstanding options and 58,295 shares of Class A common stock to be issued upon the vesting and settlement of outstanding RSUs. We have registered an aggregate of 17,845,247 shares of Class A common stock issuable (i) upon exercise of outstanding options, (ii) upon the vesting and settlement of outstanding RSUs and (iii) upon exercise or settlement of any options or other equity incentives we may grant in the future for public resale under the Securities Act. Accordingly, these shares may be freely sold in the public market upon issuance as permitted by any applicable vesting requirements, subject to the lock-up agreements described below and compliance with applicable securities laws.

In connection with this offering, we, the selling stockholders and our directors and executive officers have agreed with J.P. Morgan Securities LLC and RBC Capital Markets, LLC on behalf of the underwriters in this offering, that for 90 days after the date of this prospectus (in the case of us and the selling stockholders) or 60 days after the date of this prospectus (in the case of our directors and executive officers who are not selling stockholders), subject to certain exceptions, we and they will not, directly or indirectly, dispose of any of our common stock or securities convertible into or exercisable or exchangeable for our common stock. See the section entitled “Shares eligible for future sale” for more information.

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Sales of a substantial number of such shares upon expiration of the lock-up agreements, or the perception that such sales may occur, or early release of these agreements, could cause our market price to fall or make it more difficult for you to sell your Class A common stock at a time and price that you deem appropriate.

We may also issue shares of our Class A common stock or securities convertible into shares of our Class A common stock from time to time in connection with a financing, acquisition, investment, our employee incentive compensation plan or otherwise. Any such issuance could result in substantial dilution to our existing stockholders and cause the market price of our Class A common stock to decline.

We are a “controlled company” within the meaning of the rules of the NASDAQ Stock Market and, as a result, we qualify for, but do not currently intend to rely on, exemptions from certain corporate governance requirements. In the event that we were to rely on these exemptions in the future, you would not have the same protections as are afforded to stockholders of companies that are subject to such requirements.

Upon completion of this offering, James R. Scapa, our chairman and chief executive officer, will continue to control a majority of the combined voting power of our company. As a result, we will continue to be a “controlled company” within the meaning of the NASDAQ corporate governance standards. Under the NASDAQ rules, a company of which more than 50% of the voting power is held by an individual, group or another company is a “controlled company” and need not comply with certain requirements, including the requirement that a majority of the Board consist of independent directors and the requirements that our compensation and nominating and governance committees be composed entirely of independent directors. Since our initial public offering, we have not taken advantage of, and following this offering we do not intend to take advantage of, these exemptions. However, for so long as we qualify as a “controlled company,” we have the authority to utilize some or all of these exemptions. If we utilize these exemptions, among other things, we may not have a majority of independent directors and our compensation and nominating and governance committees may not consist entirely of independent directors. Thus, in the event that we were to rely on these exemptions in the future, you would not have the same protections as are afforded to stockholders of companies that are subject to all of the corporate governance requirements of NASDAQ.

The dual class structure of our common stock has the effect of concentrating voting control with certain stockholders who hold shares of our Class B common stock, including our founders, certain of our directors and executive officers and affiliates, who will hold in the aggregate 91% of the voting power of our capital stock following the completion of this offering. This will limit or preclude your ability to influence corporate matters, including the election of directors, amendments of our organizational documents, and any merger, consolidation, sale of all or substantially all of our assets, or other major corporate transaction requiring stockholder approval.

Our Class B common stock has ten votes per share, and our Class A common stock, which is the common stock we are offering pursuant to this prospectus, has one vote per share. Following this offering, our Class B stockholders, including our founders, certain of our directors and executive officers, and affiliates, will hold, in the aggregate 91% of the voting power of our capital stock. The ten-to-one voting ratio between our Class B and Class A common stock, results in the holders of our Class B common stock collectively controlling a majority of the combined voting power of our common stock and therefore being able to control all matters submitted to our stockholders for approval until 2029, or upon the occurrence of a triggering event at which time all shares of our Class B common stock will automatically convert into shares of our Class A common stock, or on an earlier date, as set forth in our certificate of incorporation.

This concentrated control will limit or preclude your ability to influence corporate matters for the foreseeable future, including the election of directors, amendments of our organizational documents, and any merger, consolidation, sale of all or substantially all of our assets, or other major corporate transaction requiring

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stockholder approval. In addition, this may prevent or discourage unsolicited acquisition proposals or offers for our capital stock that you may feel are in your best interest as one of our stockholders.

Future transfers by holders of our Class B common stock will generally result in those shares converting to Class A common stock, subject to the specific exceptions set forth in our certificate of incorporation, such as certain transfers effected for estate planning purposes and between or among our founders. The conversion of Class B common stock to Class A common stock will have the effect, over time, of increasing the relative voting power of those holders of Class B common stock who retain their shares in the long-term. For a description of the dual class structure, see the section entitled “Description of capital stock—Anti-takeover effects of Delaware law and our certificate of incorporation and bylaws.”

Our bylaws designate courts in the State of Delaware as the sole and exclusive forums for certain types of actions and proceedings that may be initiated by our stockholders, which could limit our stockholders’ ability to obtain a favorable judicial forum for disputes with us or our directors, officers, or employees.

Our bylaws provide that, subject to limited exceptions, a state or federal court located within the State of Delaware will be the sole and exclusive forums for:

Any person or entity purchasing or otherwise acquiring any interest in shares of our capital stock are deemed to have notice of and to have consented to these provisions. These provisions may limit a stockholder’s ability to bring a claim in a judicial forum that it finds favorable for disputes with us or our directors, officers, or other employees, which may discourage such lawsuits against us and our directors, officers, and employees. Alternatively, if a court were to find these provisions of our bylaws inapplicable to, or unenforceable in respect of, one or more of the specified types of actions or proceedings, we may incur additional costs associated with resolving such matters in other jurisdictions, which could adversely affect our business and financial condition.

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Special note regarding forward looking statements

This prospectus and the documents incorporated by reference in this prospectus, particularly in the sections titled “Prospectus Summary” and “Risk Factors” in this prospectus and the sections titled “Risk Factors,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and “Business” in our Annual Report on Form 10-K for the year ended December 31, 2017 and our Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, include forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities and Exchange Act of 1934, as amended. All statements other than statements of historical facts contained in this prospectus, including statements regarding our future results of operations and financial position, strategy and plans, market size and opportunity, competitive position, industry environment, potential growth opportunities and our expectations for future operations, are forward-looking-statements. The words “believe,” “may,” “will,” “estimate,” “continue,” “anticipate,” “design,” “intend,” “expect,” “could,” “plan,” “potential,” “predict,” “seek,” “should,” “would” or the negative version of these words and similar expressions are intended to identify forward-looking statements. We have based these forward-looking statements on our current expectations and projections about future events and trends that we believe may affect our financial condition, results of operations, strategy, short- and long-term business operations and objectives, and financial needs. These forward-looking statements are subject to a number of risks, uncertainties and assumptions described under the section titled “Risk Factors” in this prospectus and in our Annual Report on Form 10-K for the year ended December 31, 2017, as updated by our Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, which are incorporated by reference in this prospectus, and elsewhere in this prospectus and in the documents incorporated by reference in this prospectus, regarding, among other things:

These risks are not exhaustive. Other sections of this prospectus and the documents incorporated by reference in this prospectus may include additional factors that could adversely impact our business and financial performance. New risk factors emerge from time to time and it is not possible for our management to predict

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all risk factors, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in, or implied by, any forward-looking statements.

You should not rely upon forward-looking statements as predictions of future events. Although we believe that the expectations reflected in the forward-looking statements are reasonable, we cannot guarantee future results, levels of activity, performance or achievements. Except as required by law, we undertake no obligation to publicly update any forward-looking statements for any reason.

You should read this prospectus, the documents incorporated by reference in this prospectus and the documents that we have filed as exhibits to the registration statement on Form S-1, of which this prospectus is a part, that we have filed with the SEC with the understanding that our actual future results, levels of activity, performance and achievements may be materially different from what we expect.

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Market, industry and other data

We obtained the industry, market and competitive position data used throughout this prospectus from our own internal estimates and research, as well as from industry and general publications, in addition to research, surveys and studies conducted by third parties. Internal estimates are derived from publicly-available information released by industry analysts and third party sources, our internal research and our industry experience, and are based on assumptions made by us based on such data and our knowledge of our industry and market, which we believe to be reasonable. In addition, while we believe the industry, market and competitive position data included in this prospectus is reliable and is based on reasonable assumptions, such data involves risks and uncertainties and are subject to change based on various factors, including those discussed in the section entitled “Risk factors” in this prospectus and in the documents incorporated by reference in this prospectus. These and other factors could cause results to differ materially from those expressed in the estimates made by the independent parties and by us.

Information based on estimates, forecasts, projections, market research, or similar methodologies is inherently subject to uncertainties, and actual events or circumstances may differ materially from events and circumstances that are assumed in this information. In some cases, we do not expressly refer to the sources from which data is derived.

Certain information in this prospectus or in documents incorporated by reference in this prospectus is contained in independent industry publications. The source of these independent industry publications is provided below:

The independent publications described herein or in the documents incorporated by reference in this prospectus represent research opinions or viewpoints published and are not representations of fact. Each publication speaks as of its original publication date (and not as of the date of this prospectus) and are subject to change without notice.

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Use of proceeds

We estimate that the net proceeds from our sale of 3,292,580 shares of Class A common stock in this offering at an assumed public offering price of $35.19 per share, the last reported sale price of our common stock on the NASDAQ Global Select Market on May 31, 2018, after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us, will be approximately $109.9 million, or $138.1 million if the underwriters’ option to purchase additional shares is exercised in full. A $1.00 increase (decrease) in the assumed public offering price would increase (decrease) the net proceeds to us from this offering by $3.1 million, assuming the number of shares offered by us, as set forth on the front cover of this prospectus, remains the same and after deducting the estimated underwriting discounts and commissions payable by us. We will not receive any proceeds from the sale of Class A common stock by the selling stockholders; however we will receive net proceeds of $0.5 million from certain selling stockholders upon the exercise of stock options in order to sell such shares in this offering.

We intend to use the net proceeds to us from this offering for general corporate purposes, including working capital, sales and marketing activities, general and administrative matters, real estate development, including developing and building an addition adjacent to our corporate headquarters facilities, and capital expenditures. We may also use a portion of the net proceeds for the acquisition of, or investment in, technologies, solutions or businesses that complement our business. We do not have any agreements or binding commitments for any such acquisitions or investments at this time.

We will have broad discretion over the uses of the net proceeds in this offering. Pending these uses, we may invest the net proceeds from this offering in short-term, investment-grade interest-bearing securities such as money market accounts, certificates of deposit, commercial paper and guaranteed obligations of the United States government.

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Dividend policy

We have never declared or paid and do not anticipate declaring or paying, any cash dividends on our Class A common stock. We currently intend to retain all available funds and any future earnings for use in the operation of our business. Any future determination to declare dividends will be made at the discretion of our board of directors and will depend on our financial condition, results of operations, capital requirements, general business conditions and other factors that our board of directors may deem relevant.

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Market price of common stock

Shares of our Class A common stock commenced trading on the NASDAQ Global Select Market under the symbol “ALTR” on November 1, 2017. Prior to that date, there was no public market for our Class A common stock. The following table summarizes the high and low sale prices of our common stock as reported by the NASDAQ Global Select Market:

On May 31, 2018, the last reported sale price of our Class A common stock on the NASDAQ Global Select Market was $35.19 per share. As of March 31, 2018, there were approximately 465 registered stockholders of record of our Class A common stock and 5 registered stockholders of record of our Class B common stock. This figure does not reflect the beneficial ownership or shares held in nominee name.

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Capitalization

The following table shows our cash and cash equivalents and our capitalization as of March 31, 2018 on:

You should read this table together with the sections of this prospectus titled “ Summary Historical Consolidated Financial and Other Data,” and “Description of Capital Stock” and the section titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our unaudited consolidated financial statements and related notes in our Quarterly Report on 10-Q for the quarter ended March 31, 2018, which is incorporated by reference in this prospectus.

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The total number of shares of our common stock to be outstanding set forth in the table above is based on 27,357,012 shares of our Class A common stock and 36,507,676 shares of our Class B common stock, outstanding as of March 31, 2018, and excludes:

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Dilution

If you invest in our Class A common stock in this offering, your ownership interest will be diluted immediately to the extent of the difference between the public offering price per share of our Class A common stock and the as adjusted net tangible book value per share of our Class A common stock immediately after this offering.

Net tangible book value per share is determined by dividing our total tangible assets less our total liabilities by the number of shares of our common stock outstanding. Our historical net tangible negative book value as of March 31, 2018, was $(19.1) million, or $(0.30) per share. After giving effect to (i) the sale and issuance of 3,292,580 shares of our Class A common stock offered by us in this offering based on the assumed public offering price of $35.19 per share, the last reported sale price of our common stock on the NASDAQ Global Select Market on May 31, 2018, after deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us, and (ii) the issuance of 257,000 shares of our Class A common stock to certain selling stockholders upon the exercise of stock options in order to sell such shares in this offering, including net proceeds of $0.5 million received by us in connection with the exercise of such options, our as adjusted net tangible book value as of March 31, 2018, would have been $91.3 million, or $1.35 per share. This represents an immediate increase in net tangible book value of $1.65 per share to our existing stockholders and an immediate dilution in net tangible book value of $33.84 per share to investors purchasing shares of our Class A common stock in this offering at the assumed public offering price.

The following table illustrates this dilution on a per share basis to new investors:

A $1.00 increase (decrease) in the assumed public offering price of $35.19 per share, the last reported sale price of our Class A common stock on the NASDAQ Global Select Market on May 31, 2018 would increase (decrease) our as adjusted net tangible book value per share immediately after this offering by $0.05 per share and the dilution per share to new investors in this offering by $0.95 per share, assuming the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same, and after deducting underwriting discounts and commissions payable by us. Similarly, each increase of one million shares in the number of shares of Class A common stock offered by us would increase our as adjusted net tangible book value per share immediately after this offering by $0.47 per share and decrease the dilution per share to new investors by $0.47 per share, assuming the assumed public offering price remains the same and after deducting underwriting discounts and commissions payable by us. Further, each decrease of one million shares in the number of shares of Class A common stock offered by us would decrease our as adjusted net tangible book value per share immediately after this offering by $0.49 per share and increase the dilution per share to new investors by $0.49 per share, assuming the assumed public offering price remains the same and after deducting underwriting discounts payable by us.

The total number of shares of our common stock to be outstanding set forth in the table above is based on 27,357,012 shares of our Class A common stock and 36,507,676 shares of our Class B common stock, outstanding as of March 31, 2018, and excludes:

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Principal and selling stockholders

The following table sets forth certain information with respect to the beneficial ownership of our common stock as of May 15, 2018, which is referred to as the Beneficial Ownership Date, and as adjusted to reflect the sale of our Class A common stock offered by us and the selling stockholders in this offering assuming no and full exercise of the underwriters’ option to purchase additional shares from us, for:

The amounts and percentage of shares of common stock beneficially owned are reported on the basis of regulations of the SEC governing the determination of beneficial ownership of securities. Under the rules of the SEC, a person is deemed to be a “beneficial owner” of a security if that person has or shares “voting power,” which includes the power to vote or to direct the voting of such security, or “investment power,” which includes the power to dispose of or to direct the disposition of such security. In computing the number of shares beneficially owned by a person and the percentage ownership of that person, we have deemed shares of our Class A common stock subject to options that are currently exercisable or exercisable within 60 days of May 15, 2018, and shares of our Class A common stock that are reserved for settlement of RSUs that are vested or will be vested within 60 days of May 15, 2018, to be outstanding and to be beneficially owned by the person holding the option for the purpose of computing the percentage ownership of that person but have not treated them as outstanding for the purpose of computing the percentage ownership of any other person.

The percentages reflect beneficial ownership immediately prior to and immediately after the completion of this offering as determined in accordance with Rule 13d-3 under the Exchange Act and are based on 29,049,457 shares of our Class A common stock and 35,846,152 shares of our Class B common stock outstanding as of the Beneficial Ownership Date. We have based percentage ownership of our common stock after this offering assuming no exercise of the underwriters’ option to purchase additional shares of Class A common stock from us on 34,443,005 shares of our Class A common stock outstanding as of the Beneficial Ownership Date and on 34,170,732 shares of our Class B common stock outstanding as of the Beneficial Ownership Date, assuming the sale of 5,600,000 shares of our Class A common stock by us and the selling stockholders in this offering (including the shares to be issued upon the exercise of options to purchase shares of our Class A common stock and sold in this offering).

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Except as noted below, the address for all beneficial owners in the table below is c/o Altair Engineering Inc. at 1820 E Big Beaver Road, Troy MI 48083.

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