How to calculate my AMTI? I didn't get Form 6251. If I add my Taxable Income (Line 10) to my Itemized Deductions (Line 8), I get the same amount as my AGI. Is that it?

why do you need it?  the AMT calculation is mostly automatic. there will be no 6251 in your return if you are not subject to it.  if you are interested in what makes up AMTI type 6251 in the search box. it's on line 4