MAGI for what purpose? There are about a dozen different definitions of MAGI for different purposes.
Are you asking about MAGI on line 7 of Form 8582 for passive loss limitations? Why are you trying to calculate it yourself? TurboTax will calculate it for you automatically.
This online community is run by Intuit, the company that makes TurboTax, to help its customers use TurboTax to prepare their tax returns. If you are using other software, you should ask for help in the support forum for the software you are using. If you are doing your tax return by hand, the rules for calculating MAGI on Form 8582 are in the instructions for line 7 on page 10 of the IRS instructions for Form 8582.
