Sales Tax Calculator

This sales tax calculator adds or removes tax from a price in one step. Sales tax, VAT and GST calculators do two jobs: add tax to a net price to get the amount to charge, or strip tax out of an inclusive price to find the net. This tool does both from one rate, and it uses the correct reverse maths.

The maths

add tax:    gross = net × (1 + rate)
remove tax: net = gross ÷ (1 + rate)
tax = gross − net

Removing tax is a division, not a subtraction, because the rate applies to the net, not the gross.

Why the reverse matters

Subtracting the rate from an inclusive price overstates the tax and understates the net — a common error on invoices. Dividing by (1 + rate) gives the true net every time.

Worked example

A 250.00 net price at 7%:

add tax:    gross = 250.00 × 1.07 = 267.50
            tax   = 267.50 − 250.00 = 17.50
remove tax: net   = 267.50 ÷ 1.07 = 250.00

The two directions meet exactly, and that round trip is the test of a correct implementation. Now make the common mistake — take 7% of the inclusive 267.50 and subtract it — and you get 267.50 − 18.73 = 248.77. The net is wrong by 1.23 and the error widens with the rate: at 20% VAT a 120.00 gross has a true net of 100.00, while the subtraction method reports 96.00.

Rates are never just one number

The rate you enter depends on what is being sold and where. Sales tax in the United States is set by state and often by county and city as well, so a single purchase can carry a combined rate assembled from three jurisdictions, and some states exempt groceries or clothing outright. VAT across the European Union typically runs a standard rate near 20% with reduced rates for food, books and energy. GST in Australia, Canada, India and elsewhere follows the same reduced-rate pattern.

None of that changes the arithmetic here — enter the rate that applies to your transaction and the tool does the rest — but it makes the rate the input most worth double-checking. On an invoice the rate should sit next to the tax line; when it does not, derive it from the net and the tax rather than guessing.

Fixing an invoice

The reverse direction is the one that catches real errors. Given a tax-inclusive total, divide by (1 + rate) to recover the net for your accounts; never multiply. A quick sanity check follows from the formula: tax on a gross figure is always smaller than rate × gross, because the rate applies to a base that excludes the tax itself. If your number fails that test, the direction is wrong.

The same ordering question appears in Discount Calculator, where tax is applied after the discount rather than before, and Percentage Calculator covers the general case of expressing one figure as a share of another. Getting the direction right once, here, removes an entire category of bookkeeping mistakes.

Private and precise

Every figure is worked out in your browser with standard financial formulas. Nothing you type is uploaded, stored or sent anywhere.