The tax on long-term capital gain depends on your filing status, how much other income you have, what kinds of other income you have, and possibly other factors.
You can use TaxCaster to get a rough idea. Enter all your information except the capital gain and see how much the tax is. Then add the capital gain and see how much the tax increases.
TaxCaster is still set up for 2019, but it will give you a pretty good idea of how much the tax will be.
