How much
tax?

About the sales tax calculator

This calculator adds sales tax to a price, or works backwards to remove it from a total. Sales tax is a percentage charged on top of the marked price of goods and services, collected by the seller and passed on to the government. Because rates differ by country, state and even city, a quick calculator saves you from guessing what a final bill will be — or what a receipt was before tax.

How to use it

First choose what you already know. If you have the price before tax, keep “Price before tax” selected, type the amount and the tax rate, and the calculator shows the tax and the final total. For example, a $100 item at a 7.5% rate has $7.50 of tax and costs $107.50. If instead you only have the final price, switch to “Price with tax”: entering $107.50 at 7.5% recovers the $100 net price and the $7.50 of tax. Change the currency if you are shopping abroad.

The formula

Adding tax uses $T = P \cdot \frac{r}{100}$, where $P$ is the price before tax and $r$ is the rate as a percentage; the total is $P\left(1 + \frac{r}{100}\right)$. To go the other way and remove tax from a gross total $G$, divide instead: the net price is $\frac{G}{1 + r/100}$, and the tax is whatever is left over. This reverse step is why you cannot simply subtract the percentage from the total — the percentage was taken of the smaller pre-tax figure, not the total.

Where it is used

Shoppers use it to check receipts and budget for the real cost of a purchase, while small businesses use it to set shelf prices and file tax returns. It is equally useful for freelancers adding VAT to an invoice, travellers comparing prices between regions, and students learning how percentages work on top of a base amount. The reverse mode is especially handy at tax time, when you need the net figure from a total that already includes tax.