Is TurboTax calculation of my IRA contribution correct? Doesn't seem to follow IRS formula

See the link below from the IRS to determine your Modified AGI used to calculate your maximum Roth IRA contribution for 2024:  Roth IRA MAGI Calculation

After taking a closer look, if you still see a difference between the IRS calculation and the TurboTax calculation, you can provide a diagnostic copy of your tax data file so that someone here can take a closer look.  This would be the first step to determining if there is something that needs to be addressed in TurboTax.  The diagnostic file will not contain personally identifiable information, only numbers related to your tax forms.  

If you would like to provide us with the diagnostic file, follow the instructions below and post the token number along with which version of TurboTax you are using and what states you are filing in a follow-up thread.  It would be helpful to have a screenshot of the token number to prevent it from being redacted.

Use these steps if you are using TurboTax Online:

• Sign in to your account and be sure you are in your tax return.
• Select Tax Tools in the menu to the left.
• Select Tools.
• Select Share my file with agent.
• A pop-up message will appear, select OK to send the sanitized diagnostic copy to us.
• Post the token number here. 

If you are using a CD/downloaded version of TurboTax, use these steps:

• Select Online at the top of the screen.
• Select Send Tax File to Agent.
• Click OK.
• Post the token number here.

To answer your specific question, TurboTax does do the calculation correctly.  You can review the calculation on TurboTax's Roth IRA Contribution Limit Worksheet.