What line on the 1040 is the capital gains rate calculated on

[BTDretire]

This page says the rate is 0% up to $77,200 for MFJ.
 But what line on the 1040 could be as high as $77,200,
 for the 0% capital gains rate?
https://www.nerdwallet.com/blog/taxes/capital-gains-tax-rates/

[secondcor521]

Pretty sure it's line 43 "Taxable income" on the 2017 1040.

The actual calculation of the zero percent rate shows up currently in, among other places, the Qualified Dividends and Capital Gains Worksheet in the instructions for Form 1040.  See line 11 on page 44 here:

https://www.irs.gov/pub/irs-pdf/i1040gi.pdf

Note that they're rejiggering the Form 1040 so the above will almost certainly change for 2018 when we file our taxes here in about 7 months or so.

[seattlecyclone]

Yes, tax brackets are based on the "Taxable income" line. The Qualified Dividends and Capital Gains Worksheet walks you through that process.

In a nutshell, you compute your regular income by subtracting your capital gains and qualified dividends from that taxable income line. You apply the regular tax brackets to this number. Then you apply the capital gains rate to the applicable portion of your income.

Remember that the regular income combines with capital gains income to determine your capital gains rate. If the sum of these is over $77k (or whatever the exact number is), further capital gains will be taxed at 15% regardless of what fraction of your first $77k was capital gains.