Sales tax sneaks onto almost every purchase in the U.S., but the listed price rarely includes it. Knowing how to add it yourself — or peel it back out of a total — helps you budget, check receipts, and price items correctly if you sell. The arithmetic is quick once you know the two directions it can go.
Adding sales tax to a price
To find the tax and the total from a pre-tax (net) price:
- Tax = Price × (Tax Rate ÷ 100)
- Total = Price + Tax
Example: A jacket costs $80 and the local sales tax rate is 8.25%.
- Tax = $80 × 0.0825 = $6.60
- Total = $80 + $6.60 = $86.60
You can also combine the steps by multiplying by (1 + rate): $80 × 1.0825 = $86.60.
Working backward from a tax-inclusive total
Sometimes you only know the final amount and want the original price — useful for expense reports or bookkeeping. The trick is to divide, not subtract:
- Net Price = Total ÷ (1 + Tax Rate)
- Tax = Total − Net Price
Example: You paid $86.60 total and the rate was 8.25%.
- Net Price = $86.60 ÷ 1.0825 = $80.00
- Tax = $86.60 − $80.00 = $6.60
A common mistake is subtracting 8.25% of the total instead of dividing — that gives the wrong answer because the tax was calculated on the smaller net price, not the total.
Sales tax rates vary by location
There's no single national sales tax in the United States. Rates are set by states, counties, and cities and then stacked together, so the rate at checkout can differ from one town to the next. A handful of states (like Oregon and Delaware) have no state sales tax at all. Always use the combined rate for the exact location where the sale happens.
How to use it
Rather than juggle decimals, let the Sales Tax Calculator do both directions. Enter a price and rate to add tax, or enter a tax-inclusive total to back out the original price and the tax amount.
This pairs naturally with two other everyday tools:
- The Discount Calculator finds the sale price after a percentage off — apply it before tax to see your real out-the-door cost.
- The Tip Calculator handles the other line item that gets added at restaurants, so you can plan the full total in seconds.