Federal Income Tax Use this calculator to estimate your income tax liability along with average and marginal tax rates. You are viewing this website at a small screen resolution which doesn't support calculators. Click here to view this calculator. Related Content Changing Unhealthy Behaviors Five phases to changing unhealthy behaviors. Choosing a Business Structure Entrepreneurs all face the same question, “Which business structure should I adopt?” The Facts About Income Tax Millions faithfully file their 1040 forms each April. But some things about federal income taxes may surprise you.