Your conclusion is incorrect. The capital gains are added to your other taxable income to determine what capital gains tax bracket you are in. You would have 3 different capital gains tax rates on $500,000 of long term capital gains--0%, 15% and 20%.
Here are the capital gains tax brackets for each range of taxable income including the capital gains amount:
Tax rate Single Joint Head of household
0% $0 to $38,600 $0-$77,200 $0-$51,700
15% $38,601-$425,800 $77,201-$479,000 $51,701-$452,400
20% $425,801 and up $479,001 and up $452,401 and up
There is also a Net Investment Income Tax of 3.8% that applies in incomes above certain thresholds. See this IRS pub for the threshold amounts: <a rel="nofollow" target="_blank" href="
https://www.irs.gov/newsroom/questions-and-answers-on-the-net-investment-income-tax">https://www.irs...>
