If your taxable income is $80,800 or less (for 2021, married filing jointly), there is no tax on your long-term capital gains. Unemployment or wages do not make any of the long-term capital gain taxable, as long as your total taxable income is $80,800 or less.
The percentage of your Social Security that is taxable depends on your other income. The additional income from the capital gain might have made more of your Social Security taxable, which would increase your tax, even though there is still no tax on the long-term capital gain itself.
You might also double-check your entries. Make sure you entered the capital gain as long-term, and make sure the entries for all your other income are correct.
What do you mean by the "TurboTax calculator"? Are you referring to TaxCaster, or the TurboTax 2021 software itself, or something else?
