Two sales-tax questions come up constantly: how much tax to add to a price, and how to back out the tax from a total that already includes it. Both are short formulas, shown below with examples. The free sales tax calculator does either instantly.
How US sales tax works
The United States has no national sales tax. Instead, states, counties and cities each set their own rates, so the combined rate at the register varies by location — from 0% in a handful of states to over 10% in some cities. Always use the combined rate for wherever the sale happens.
Adding sales tax to a price
Tax = price × (rate ÷ 100)
Total = price + tax
Example — a $100 item at 7.25%. Tax = 100 × 0.0725 = $7.25, so the total is 100 + 7.25 = $107.25.
Removing sales tax from a total (reverse)
If you only know the tax-inclusive total and want the pre-tax price, you can't just subtract the percentage of the total — that overcounts. Divide instead:
Pre-tax price = total ÷ (1 + rate ÷ 100)
Tax = total − pre-tax price
Example — $107.25 including 7.25% tax. Pre-tax = 107.25 ÷ 1.0725 = $100, so the tax portion is 107.25 − 100 = $7.25. Notice 7.25% of $107.25 would be $7.78 — the wrong answer, which is exactly why you divide rather than multiply.
FAQ
How do I find the pre-tax price from a receipt total? Divide the total by (1 + rate ÷ 100). At 7.25%, divide by 1.0725.
Why can't I just subtract 7.25%? Because 7.25% of the inclusive total is larger than the actual tax — the tax was charged on the smaller pre-tax price, not the total.
What rate should I enter? The combined state + county + city rate for the location of the sale. A quick search for your ZIP code's sales tax rate gives the figure.
Is my data private? Yes — the calculator runs in your browser and stores nothing.