Sales Tax Calculator
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About Sales Tax Math
Sales tax touches nearly every US purchase, yet two calculations trip people constantly: what a listed price will really cost at the register, and — for expense reports, budgets, and resellers — how much of a receipt total was tax. The second one has a genuinely counter-intuitive formula, which is why spreadsheets full of subtracted percentages are quietly wrong.
Pick a direction, enter the amount and your local combined rate, and get the tax and the answer with its working. The reverse mode is the one accountants call “backing out” tax — used for invoices, VAT-style receipts, and any time a total is tax-inclusive.
Working with value-added tax abroad instead? That's the VAT Calculator
Both Directions, Done Right
The forward direction is obvious; the reverse is the one worth memorizing:
Add tax: total = price × (1 + rate/100) Back out: price = total ÷ (1 + rate/100) ← divide, don't subtract! tax = total − price
Worked example: $100 at 8.25% → $8.25 tax, $108.25 total. Reversing: $108.25 ÷ 1.0825 = $100.00 exactly. The wrong way — subtracting 8.25% from $108.25 — gives $99.32, and that 68-cent error compounds across every line of an expense report.
Tax per $100 at Common Rates
Combined state + local rates across the US mostly land between 5% and 10% — the register math at each:
| Combined rate | Tax on $100 | Total |
|---|---|---|
| 5% | $5.00 | $105.00 |
| 6% | $6.00 | $106.00 |
| 7% | $7.00 | $107.00 |
| 8% | $8.00 | $108.00 |
| 8.25% | $8.25 | $108.25 |
| 9% | $9.00 | $109.00 |
| 10% | $10.00 | $110.00 |
The mental shortcut: the rate IS the dollars per hundred — 8.25% means $8.25 on every $100, so a $450 purchase carries about 4.5 × $8.25 ≈ $37 of tax.
How US Sales Tax Actually Works
Your rate is a stack: a state rate plus county, city, and special-district add-ons, which is why the combined figure differs across a metro area and can pass 10% in some cities. Five states charge no statewide sales tax at all — New Hampshire, Oregon, Montana, Delaware, and Alaska (which allows local rates). Groceries, clothing, and medicine get reduced or zero rates in many states, so one receipt can carry two different rates legitimately.
Online purchases now generally charge the rate at your delivery address (post-2018 Wayfair rules), so the days of tax-free carts are mostly gone. For the exact combined rate where you live, your state revenue department publishes lookup tools — enter that figure here and the math is done at your true rate, never a stale average.
Frequently Asked Questions
How do I calculate sales tax?
Multiply the price by the rate as a decimal: $100 × 0.0825 = $8.25 tax, $108.25 total at an 8.25% combined rate. Enter your own local rate above — combined state + local rates vary from 0 to over 10%.
How do I take sales tax out of a total?
Divide the total by 1 + the rate: $108.25 ÷ 1.0825 = $100 pre-tax. Never subtract the percentage from the total — the tax was computed on the smaller pre-tax number, so subtraction always over-removes.
Which states have no sales tax?
New Hampshire, Oregon, Montana, and Delaware have no state or local sales tax; Alaska has no statewide tax but permits local rates. Everywhere else, expect a combined state + local rate — commonly 5–10%.
Why does my receipt show a different rate than the state rate?
Because you pay the combined rate: state + county + city + any special districts (transit, stadium). Two stores a mile apart can charge different totals across a city line. Your receipt's rate is the real one for that address.
Do I pay sales tax on online orders?
Usually yes, at your delivery address's combined rate — since the 2018 Wayfair decision, states can require out-of-state sellers to collect. Small sellers under a state's threshold may not collect, in which case use-tax rules technically put the obligation on you.
Is sales tax charged on the discounted or original price?
On what you actually pay the retailer: after store discounts and coupons the register applies, before manufacturer rebates you claim later. Gift-card purchases aren't taxed when buying the card — tax hits when the card buys goods.
Methodology. This calculator uses standard financial formulas used across the industry. It is reviewed and maintained by the Vast Calculators editorial team.
Last updated · July 10, 2026
Disclaimer. This tool provides estimates for general informational purposes only and is not a substitute for professional financial advice. Always consult a qualified financial advisor before making decisions about your finances.