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Sales Tax by Amount Calculator

Add sales tax to any price instantly

How it is calculated

The tool adds a sales tax to a price that does not yet include it: tax = price × rate ÷ 100 and total = price + tax. Price is the pre-tax amount and rate is the tax percentage you type, for example 8.25 for 8.25%. Neither can be negative. The rate is not looked up for you: sales tax and VAT rates differ by country, state and product category, so enter the rate that applies to your purchase. To go the other way, from a tax-inclusive price back to the pre-tax amount, divide by 1 + rate ÷ 100 instead.

Worked example

An item costs 120 before tax and the rate is 8.25%. Tax: 120 × 8.25 ÷ 100 = $9.90. Total: 120 + 9.90 = $129.90. The extra 9.90 is what the seller collects on behalf of the tax authority.

Try this example →

Common mistakes

  • Applying the rate to a price that already includes tax, which charges tax twice. For a tax-inclusive price, divide by 1 + rate ÷ 100.
  • Entering the rate as a decimal such as 0.0825. The field expects a percentage, 8.25.
  • Using the headline rate for every item. Food, books or services may have a reduced rate or none.
  • Forgetting local add-on taxes, such as city or county rates, which may be on top of the state rate.

About this calculator

Adding sales tax is a two-step calculation: tax amount = price × tax rate, then total = price + tax amount. It sounds trivial, but U.S. sales tax rates are set locally and stack — a combined state, county, and city rate can range from 0% in Oregon or Montana to over 10% in parts of California, Louisiana, or Illinois — so the "right" rate depends entirely on where the sale happens.

Retail cashiers, online sellers configuring checkout rules, and shoppers estimating a final receipt total all use this same calculation. Bookkeepers also run it in reverse to verify that a posted tax line matches the rate that should have applied to a given transaction.

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