Tax calculator, tables, rates. Calculate your 2018 tax. Quickly figure your 2018 tax by entering your filing status and income. Tax calculator is for 2018 tax year only. Do not use the calculator for 540 2EZ or prior tax years. Based on these rates, this hypothetical $50,000 earner owes $6,858.50, an effective tax rate of 13.7%. Calculating Taxable Income Using Exemptions and Deductions. Of course, calculating how much you owe in taxes is not quite that simple. For starters, federal tax rates apply only to taxable income. Your effective tax rate would be 15%, or $9,057 divided by $60,000. The taxpayer with $80,000 in taxable income would have an effective tax rate of almost 17%: $13,457 divided by $80,000. But you both have the same marginal tax rate of 22%.