Sales Tax Calculator
With amount 100 usd, sales tax rate 8.25 percent, sales tax comes to $108.25 — total with tax. It is reached in 4 steps, the last of which is 100 + 8.25, and each one is printed on the page with its numbers filled in. The formula is the one published by Federation of Tax Administrators, not an approximation fitted to it.
Tax and total from a pre-tax price, plus the reverse — the pre-tax price hidden inside a total you already paid.
Formula and sources checked · How we check
Amount 100, Sales tax rate 8.25
$108.25
Total with tax for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Tax on that amount
100 * 8.25 / 1008.25- Total with tax
100 + 8.25108.25- If that amount already included tax, the pre-tax price was
100 / (1 + 8.25 / 100)92.379- …and the tax inside it was
100 - 92.3787537.621
Worked example
$100 plus 8.25% is $108.25. Run it the other way and a $100 receipt that already included 8.25% tax breaks down to $92.38 plus $7.62 — not $91.75, because the tax was charged on the smaller base.
How to work it out yourself
- 1.Enter the price before tax and the combined rate for the address the sale happens at. State, county and city rates stack, and the total is often well above the state figure alone.
- 2.To work backwards from a receipt, divide by one plus the rate rather than subtracting the percentage. Taking 8.25% off a tax-inclusive total is the commonest way to get this wrong.
- 3.The tax base is the price after discounts and, in most states, after a trade-in allowance. Shipping is taxable in some states and not in others.
The formula
- Tax on that amount
100 * 8.25 / 100 - Total with tax
100 + 8.25 - If that amount already included tax, the pre-tax price was
100 / (1 + 8.25 / 100) - …and the tax inside it was
100 - 92.378753
Source: Federation of Tax Administrators — state sales tax rates, Streamlined Sales Tax Governing Board
Questions people actually ask
- Why is reverse sales tax not just subtracting the rate?
- The rate applies to the pre-tax price, not the total. Taking 8.25% off $100 gives $91.75, but the correct answer is $92.38 — divide by 1.0825 rather than multiplying by 0.9175. The gap widens with the rate.
- Which rate applies to my purchase?
- In most states, the rate at the delivery address, combining state, county, city and special-district levies. That is why a single state can have hundreds of distinct rates and why the number on the receipt rarely matches the headline state rate.
- Is everything taxable?
- No. Most states exempt or reduce tax on groceries and prescription drugs, and several exempt clothing below a threshold. Apply the rate only to the taxable portion of a mixed basket.
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