Sales Tax Calculator

How to use this calculator

In add tax mode, enter the price before tax and your local sales-tax rate to get the tax amount and the final total. In remove tax mode, enter a total that already includes tax and the rate, and the tool works backwards to show the original pre-tax price and how much of the total was tax. It is handy for budgeting against advertised prices, checking a receipt, or pricing items where you need a round total after tax.

The formula explained

Sales tax is a percentage added on top of the price:

total = price × (1 + rate ÷ 100) · price = total ÷ (1 + rate ÷ 100)

To add tax, you turn the rate into a decimal, add one, and multiply the price — the "add one" keeps the original price and adds the tax on top in a single step. To remove tax you reverse it by dividing the total by that same factor. This is why you cannot simply subtract the tax percentage from a tax-inclusive total: the percentage was taken of the smaller pre-tax price, not the larger total.

A worked example

A $120 item at an 8.25% sales-tax rate has a tax of 120 × 0.0825 = $9.90, for a total of $129.90. Going the other way, if a receipt total is $129.90 at 8.25%, the pre-tax price is 129.90 ÷ 1.0825 = $120, confirming the tax was $9.90.

Frequently asked questions

How do you add sales tax?

Multiply the price by the rate ÷ 100 for the tax, then add it to the price.

How do you remove tax from a total?

Divide the total by one plus the rate as a decimal to get the pre-tax price.

What is the tax amount?

The difference between the tax-inclusive total and the pre-tax price.