Sales Tax Calculator

How to add sales tax to a price

Enter the pre-tax amount and your combined sales tax rate. The tool multiplies the two and shows the tax due plus the total including tax.

The rate is entirely up to you, which is what lets one page cover every US jurisdiction as well as VAT-style rates elsewhere. It also means the accuracy of the answer is only as good as the rate you look up.

• Enter the price before tax in the Amount (before tax) field. It starts at 100.
• Enter your combined state, county, and city rate in the Sales tax rate (%) field. It starts at 8.5.
• Read the Sales tax line for the amount owed and Total with tax for the register total.
• If the item is discounted, apply the discount first and enter the reduced price here.
• To reverse a tax-inclusive figure, divide it by 1 plus the rate as a decimal outside the tool.

Why you enter the rate yourself

This is a generic-rate calculator, not a jurisdiction lookup. It has no database of state, county, city, or special-district rates, no zip code field, and no address matching. It multiplies the number you type by the percentage you type. If the rate is wrong, the answer is wrong, and the tool has no way to know.

That design has one real advantage. Rate tables go out of date the moment a transit district passes a levy or a state changes its base rate, and a stale table produces a confidently wrong number. Here the only source of truth is the rate you looked up, which you can verify against your state revenue department before you type it.

The rate to enter is the combined one. US sales tax stacks a state rate, a county rate, a city rate, and sometimes a special-district rate, so a 6.25 percent state figure can arrive at the register as 9 percent or more. Entering the state rate alone undercounts in most metro areas.

• No zip, city, state, or address lookup of any kind.
• No product exemptions for groceries, clothing, or prescriptions.
• No cart, no line items, and no per-item rates.
• Combined state plus local rate is what belongs in the rate field.

Working backwards from a tax-inclusive total

The tool runs forward only, from a pre-tax amount to a total. To strip tax out of a figure that already includes it, divide by 1 plus the rate as a decimal. A 108.50 total at 8.5 percent came from 108.50 / 1.085 = 100.00, and the tax portion was 8.50.

The common mistake is to multiply the gross figure by 0.915, which gives 99.28 and is wrong by more than a dollar. The percentage was applied to the smaller number, so undoing it needs a division, not a subtraction of the same percentage. The Percentage Calculator has the general form of that reversal if you want to see it worked through.

Order matters when a discount is involved. Tax is assessed on what you actually pay, so run the Discount Calculator first and bring the reduced price here. On a 25 percent discount off 80, tax is charged on 60, not on 80.

• Forward: 100 at 8.5 percent gives 8.50 of tax and 108.50 total.
• Backward: 108.50 / 1.085 = 100.00 pre-tax.
• Wrong: 108.50 x 0.915 = 99.28, which is not the pre-tax price.
• Discount first, then tax, which is the order used at the register.