How do I calculate, or on what form does TurboTax Calculate, my modified adjusted gross income (MAGI)?

For what?  There are several different MAGI amounts for different things.  No Turbo Tax doesn’t list the MAGI on any form.  

MAGI is calculated differently for different purposes. There are about a dozen different definitions of MAGI, depending on what it's being used for.

What do you need your MAGI for?

For most purposes the details of the MAGI calculation are not shown in TurboTax. The calculation is done behind the scenes. Even the calculated MAGI amount might not appear in TurboTax, unless it's required on an IRS form. There is only one situation where TurboTax has a worksheet for calculating MAGI, and it's a very uncommon situation.

There are also a few places where MAGI is used that are not anywhere on a tax return at all, such as for Marketplace health insurance ("Obamacare") and for calculating Medicare premiums for high-income people.