Finance · 4 min read

How to Calculate Sales Tax (US Guide)

Sales tax calculation is a single multiplication: multiply the price by the tax rate, then add that to the price for your total. The sales tax calculator does this for any state and rate combination, but the math behind it takes seconds to do by hand once you know the rate.

The basic formula

Convert the tax rate to a decimal by dividing by 100, multiply it by the price to get the tax amount, then add that to the original price for the total.

• Price: 50.00
• Tax rate: 8%
• Tax amount: 50.00 x 0.08 = 4.00
• Total: 54.00

Why the rate varies so much

Unlike VAT, there is no federal sales tax in the US. Rates are set at the state level, and many cities and counties add their own local tax on top, so the combined rate on the same purchase can differ by several percentage points from one zip code to the next, even within the same state.

States with no sales tax

Five states currently charge no statewide sales tax: Alaska, Delaware, Montana, New Hampshire and Oregon. Alaska does allow local governments to levy their own sales tax, so a purchase there can still carry tax depending on the city or borough.

Finding the combined rate

To calculate tax on a purchase, add the state rate and any local rate together before applying the formula. A state rate of 6.5% plus a local rate of 1.5% gives a combined 8% rate, applied the same way as a single rate.

Working backward from a receipt total

If you only have the final total and want to find the pre-tax price, divide the total by 1 plus the tax rate as a decimal. A total of 54.00 at an 8% rate gives 54.00 divided by 1.08, which is 50.00, and subtracting that from the total gives the 4.00 tax amount.

Tax on large or repeated purchases

The percentage stays the same regardless of price, so the tax on a 500.00 purchase at 8% is exactly ten times the tax on a 50.00 purchase: 40.00 instead of 4.00. There is no threshold where the rate changes based on amount, the way income tax brackets work.

Sales tax versus VAT

Sales tax and VAT both add a percentage to a price, but they are collected differently. Sales tax is charged once, at the final point of sale to the consumer, and businesses further up the supply chain generally do not pay it on materials they resell. VAT, used in the UK and much of the world, is collected at each stage of production, with businesses reclaiming what they have already paid. The end result for the shopper looks similar, a percentage added to the price, but the mechanics behind the scenes differ.

Rounding on tax amounts

Tax amounts are usually rounded to the nearest cent per transaction rather than calculated to several decimal places. On a price of 19.99 at a 7.25% rate, the raw tax works out to 1.449275, which rounds to 1.45, giving a total of 21.44. Adding several separately-taxed items and rounding each one can occasionally produce a cent or two of difference compared to taxing the combined total at once, which is why receipts sometimes show slightly different totals than a quick mental calculation.

Frequently asked questions