September 5, 2024

Matthew Brown
Chief Financial Officer
Altair Engineering Inc.
1820 East Big Beaver Road
Troy, MI 48083

       Re: Altair Engineering Inc.
           Form 10-K for the year ended December 31, 2023
           Form 8-K dated August 1, 2024
           File No. 001-38263
Dear Matthew Brown:

       We have limited our review of your filing to the financial statements
and related
disclosures and have the following comments.

       Please respond to this letter within ten business days by providing the
requested
information or advise us as soon as possible when you will respond. If you do
not believe a
comment applies to your facts and circumstances, please tell us why in your
response.

       After reviewing your response to this letter, we may have additional
comments.

Form 10-K for the year ended December 31, 2023
Management's Discussion and Analysis of Financial Condition and Results of
Operations
Recurring Software License Rate, page 55

1.     Please revise to state that the recurring software license rate measure
is intended to
       convey the percentage of software billings that are recurring in nature,
and to explain why
       such information is useful to investors and how management uses the
metric in managing
       or monitoring the performance of the business, consistent with what you
indicated in
       response to comment 1 in your letter dated June 30, 2022, and what you
appear to
       disclose, in part, in your Forms 10-Q.
 September 5, 2024
Page 2
Form 8-K dated August 1, 2024
Exhibit 99.1

2.     We note you present the period-over-period percentage fluctuation in
both non-GAAP net
       income and adjusted EBITDA without equal or greater presentation of the
associated
       period-over-period fluctuation in GAAP net income. Please revise
accordingly. Refer to
       Item 10(e)(1)(i)(A) of Regulation S-K and Question 102.10 of the
Non-GAAP C&DIs.
3.     We note your definition of non-GAAP diluted common shares includes the
diluted
       weighted average shares outstanding per GAAP regardless of whether you
are in a loss
       position. Please explain what this means and how you considered whether
this results in a
       measure that substitutes individually tailored measurement methods for
that of GAAP. In
       this regard, for GAAP purposes no potential common shares shall be
included in the
       computation of any diluted per share amount when a loss exists. Refer to
Question 100.04
       of the Non-GAAP C&DIs.
4.     We also note that GAAP and non-GAAP diluted shares outstanding differ
when there is
       net income on both a GAAP and non-GAAP basis, such as for the six months
ended June
       30, 2024. Please explain how non-GAAP diluted shares outstanding are
calculated for this
       period, specifically noting the differences from GAAP diluted shares
outstanding, and
       whether such differences result in a measure that substitutes
individually tailored
       measurement methods for that of GAAP.

       In closing, we remind you that the company and its management are
responsible for the
accuracy and adequacy of their disclosures, notwithstanding any review,
comments, action or
absence of action by the staff.

       Please contact Brittany Ebbertt at 202-551-3572 or Melissa Kindelan at
202-551-3564
with any questions.



                                                          Sincerely,

                                                          Division of
Corporation Finance
                                                          Office of Technology
cc:   Brian Gayle