US sales tax is added at the register and varies by state, county and city — from zero in Delaware, Montana, New Hampshire and Oregon to over 10% in some California cities. This calculator adds tax to a pre-tax price or removes it from a total that already includes tax (the "reverse" mode).
Adding tax
Tax amount = Price × Rate; Total = Price × (1 + Rate). On $100 at 8.25% (close to the national average combined rate): $8.25 tax, $108.25 total. Set the rate to your state and locality — combined rates run from 0% to about 10%.
Removing tax (reverse mode)
When a price already includes tax: Pre-tax = Total ÷ (1 + Rate). A $108.25 receipt at 8.25% tax means $100.00 of goods and $8.25 of tax. This is how businesses book revenue and how you can see the true price behind a tax-inclusive sticker.
Who charges what
State base rates range from 0% to 7.25% (California), with local add-ons pushing combined rates in some cities past 9–10%. Five states have no state sales tax at all. Online purchases: large sellers collect tax based on the delivery address in most states since the 2018 Wayfair ruling.