How to Calculate Ohio State Income Tax. The state of Ohio uses a relatively complex system to calculate residents' income taxes. Ohio has nine different income brackets, with its income tax rates increasing proportionately with higher income levels.

Know the Ohio Income Tax Brackets
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Pay low taxes on incomes below about $5,000. The tax rate for this bracket is 0.743 percent. A $5,000 income pays just $37.15 in tax.
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Pay the 1.486-percent rate if your income is approximately $5,000 or more but less than $10,000.
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Calculate what you owe using the 2.972-percent rate, which the state of Ohio stipulates is to be applied to incomes ranging from about $10,000 to $15,000.
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Use the fourth-bracket rate of 3.715 percent if your taxable income is approximately $15,000 to $20,000.
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Fall into the 4.457-percent bracket if you made more than approximately $20,000, but less than $40,000, in taxable earnings.
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Get taxed at the 5.201-percent rate if you made under approximately $80,000, but at least $40,000.
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Pay up at the higher rate of 5.943 percent if you earned approximately $80,000 to $100,000.
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Apply the second-highest tax rate, 6.9 percent, to incomes of approximately $100,000 to $200,000.
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Take the 7.5-percent tax hit if you fall into the highest tax bracket: approximately $200,000 and up.
Figure Your Ohio State Income Taxes
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Figure out your total income, using money earned through employment, business ventures, capital gains, inheritances, winnings, grants and anything else that is considered personal income. The company you work for will provide you with a W-2 statement at tax time.
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Calculate the sum of your tax deductions. Get professional help if you have trouble navigating the complex seas of personal tax deduction regulations.
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Find your total taxable income by subtracting your deductions from your income.
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Apply the appropriate tax rate to the income you earned. For example, suppose you made a total of $38,500 in taxable income. This puts you in the 4.457-percent bracket, meaning you would have to pay about $1,700 in state income tax.