Sales tax formula
Sales tax = pre-tax price × (tax rate ÷ 100)
First identify the applicable rate. Multiply the price by the rate as a decimal, and add the tax to the original price.
Worked example
- Price before tax: $45.
- Tax rate: 8% = 0.08.
- Tax: $45 × 0.08 = $3.60.
- Final total: $48.60.
Working backward
If you know only a tax-inclusive total, divide it by one plus the tax rate expressed as a decimal. A simple subtraction of the tax percentage from the total is not the same calculation.
Different locations may have exemptions or combined local rates. Our tools are mathematical estimators, not tax advice.