Sales Tax Calculator

What is a sales tax calculator?

A sales tax calculator applies a U.S. state’s base rate to a purchase amount — either to add sales tax to a pre-tax subtotal or to reverse sales tax out of a tax-included total. Statewide rates run from 0% to 7.25%.

How this calculator works

• Enter a dollar amount and pick a mode: add sales tax to a pre-tax subtotal, or reverse sales tax out of a total that already includes it.
• Select a U.S. state and its statewide base rate loads automatically — from 0% in the five states with no state sales tax up to California’s 7.25%.
• If you know the exact rate for your address, type it into the custom rate field — it overrides the state rate.
• Results show the tax in dollars, the final total (or pre-tax subtotal), and the effective rate used.

One caveat: those are state-level rates only. Counties, cities, and special districts stack 0–5+ points on top in most states, so the combined sales tax at the register usually runs higher than what a state-level tax calculator shows. A few statewide base rates for scale:

How to use the result

1. Treat the number as a floor. If the state rate is 6.25% but your address collects 8.25% combined, tax on a $400 purchase is $33, not $25 — check your state’s revenue department site for the exact local rate.
2. On a financed purchase, sales tax is charged on the full price and rolls into the amount you borrow — see how that changes the monthly math on tax on a car purchase.
3. If you’re a seller quoting customers, confirm your local rate first, then use it to add tax to a bill so the invoice matches the register.
4. In Alaska, Delaware, Montana, New Hampshire, or Oregon, don’t assume zero — some Alaskan municipalities and a few Montana resort areas levy local rates of their own.

How accurate is a sales tax calculator?

Exact for the state sales tax rate, incomplete for the real world. Most purchases are taxed at the combined rate — state plus county, city, and district — and those local layers differ by address, sometimes block by block. A state with a 6.5% base can collect 9% or more at the register. That’s why a custom rate field exists: once you know your address’s true combined rate, plug it in and the math is exact.

Common mistakes

• Assuming the state rate is what you pay. Local add-ons change that; the register total is usually higher than the state rate alone suggests.
• Backing tax out by subtraction. To reverse sales tax from $107.25 at 7.25%, divide by 1.0725 — don’t subtract 7.25%. Subtraction gives $99.47; the true pre-tax price is $100.
• Treating the five “no-tax” states as tax-free everywhere. Alaska, Delaware, Montana, New Hampshire, and Oregon have no statewide rate, but locals in parts of Alaska and Montana still charge their own.
• Ignoring exemptions. Many states exempt groceries, clothing, or prescriptions, so applying the flat rate to those baskets overstates the tax.

The arithmetic is simple — pre-tax amount × (1 + rate) = total. The hard part is knowing which rate applies at your address. To sanity-check a receipt, compute a percentage of a total and compare it with the effective rate shown above.