It all depends on the tax rate you fall in. If you are married filing joint you have to be bringing in about 480k for your capital gains tax rate to be at 20%.
If your T.I. is 77k to 479k you will be taxed at 15%.
If your T.I. is 0 to 76k you tax rate is actually 0%.
This is all married filing joint. It is different if you are single. But either way it varies depending on your taxable income.