Capital Gains Tax Estimator Use this calculator to estimate your capital gains tax. You are viewing this website at a small screen resolution which doesn't support calculators. Click here to view this calculator. Share | Have A Question About This Topic? Name Email Address Question Thank you! Oops! Related Contents The Facts About Income Tax Millions faithfully file their 1040 forms each April. But some things about federal income taxes may surprise you. How Income Taxes Work A quick look at how federal income taxes work. Federal Income Tax Use this calculator to estimate your income tax liability along with average and marginal tax rates.