What is added to income first LT or ST capital gains?

[Pacun]

If a married filing jointly return has $100K W2 income and then they have $1 million short term capital gains and $1 million Long Term Capital gains, which $1million is added first to the $100K?

Is there a place where I can find out how income listed on 1040 is added to the income pile and tax bracket applied?

[jklcpa]

21 minutes ago, Pacun said:

If a married filing jointly return has $100K W2 income and then they have $1 million short term capital gains and $1 million Long Term Capital gains, which $1million is added first to the $100K?

Is there a place where I can find out how income listed on 1040 is added to the income pile and tax bracket applied?

The place to find out is looking at the Sch D Tax Worksheet in the instructions to Sch D.  Scroll to the bottom of the index at the left of that page I linked and you'll see the Tax Worksheet is the last item listed.

In your scenario above, I believe the long-term would be what is used in the calculation because the first reference to starting to carve out gains receiving the preferential cap gain rate is where it says that lines 15 and 16 must both be gains, and on line 7 of the Sch D Tax Worksheet you enter the smaller of the lines 15 and 16, and that means the LTCG on line 15 of Sch D in the case you presented. 

That's a very general explanation and you should work through the worksheet or run a tax projection from last year's program because there are a lot of figures that factor into this calculation.