How sales tax changes a price

Multiply the taxable price by the rate

Convert the percentage rate to a decimal, multiply by the taxable price, then add the tax amount to that price.

A checkout rate may combine jurisdictions

State, county, city, and special-district components can contribute to the rate. Some goods and services are exempt or treated differently.

Use an official current rate

Do not infer a current rate from an old receipt or a national average. Confirm the location, product category, and effective date with the relevant state or local authority.

Scope: Practical Atlas performs the math you enter; it does not determine taxability or provide tax advice.

Working backward from a total

To recover the pre-tax price from a receipt total, divide by one plus the rate. Subtracting the rate from the total gives the wrong answer.

A total of $108.25 at 8.25% divides back to $108.25 ÷ 1.0825 = $100.00, so the tax was $8.25. Taking 8.25% off the total instead gives $108.25 − $8.93 = $99.32, which is wrong by 68 cents, because the tax was charged on the price, not on the total.

The rule holds for any rate: the total is the price multiplied by (1 + rate), so the price is the total divided by (1 + rate), and the tax is the difference between them.

Discounts, coupons, and delivery charges

Tax is charged on the taxable price, which is not always the sticker price.

A store discount applied at the register usually lowers the price the tax is calculated on. Manufacturer coupons, shipping and delivery charges, installation, and bundled services are treated differently from state to state, and sometimes from product to product within one state.

Because those rules vary, the calculator applies the rate to whatever price you enter. If you are unsure whether a discount or a delivery fee belongs in the taxable price, check the rule with the relevant state tax agency. The Federation of Tax Administrators keeps a directory of every state tax agency.