Free tool for US ZIP codes
Reverse Sales Tax Calculator
Enter a ZIP code and a total that already includes sales tax to see the price before tax and how much of the total is tax.
Results
Enter a ZIP code to see its combined state, county, city and district rate.
Back tax out of a total
Look up a rate, then enter a total to see the tax in it.
This is an estimate based on location alone. The tax you owe also depends on what you sell, who you sell to and the exact delivery address. If you intend to rely on these rates, use the Kintsugi platform (opens in a new tab).
How reverse sales tax is calculated
Sales tax is a percentage of the price before tax, so a total with tax is the price times (1 + rate). To go back, divide the total by (1 + rate); the tax is whatever is left.
For example, the combined rate in downtown Chicago (ZIP 60601) is 10.5%. A $221.00 total there is $221.00 ÷ 1.105 = $200.00 before tax, so the sales tax is $21.00.
The calculator rounds the price before tax to the nearest cent and gives the rest of the total as tax, so the two always add up to what you entered. Rates are by ZIP code and as of September 2026. To add tax to a price instead, use the sales tax calculator, and for the forward formula with more examples, see how to calculate sales tax.
Frequently Asked Questions
