Tax Calculator – Add or Remove Tax
Enter an amount and a tax rate to add tax to a price, or to work back from a price that already includes tax. You choose the rate and the rounding; no country's rates are built in.
How the tax is calculated
Enter the tax rate yourself. The tool does not know any country's rates, so it works for US sales tax, VAT in the UK and Europe, GST and similar taxes that are charged as a percentage of the price. The currency does not matter either: the amounts are plain numbers with up to 2 decimal places.
- Adding tax: tax = price before tax × rate ÷ 100, rounded once to the smallest currency unit. Price after tax = price before tax + tax.
- Removing tax: tax = price after tax × rate ÷ (100 + rate), rounded once. Price before tax = price after tax − tax.
The tax is rounded only once, at the end. The tool works with whole numbers of the smallest currency unit (for example, cents), so there is no floating-point error: 0.1 + 0.2 stays 0.3.
Examples
These use plain numbers; the currency does not matter.
| Task | Rate | Result |
|---|---|---|
| Add tax to 100.00 | 20% | tax 20.00, price after tax 120.00 |
| Add tax to 19.99 | 8.875% | tax 1.77 (1.7741 rounded), price after tax 21.76 |
| Remove tax from 120.00 | 20% | tax 20.00, price before tax 100.00 |
| Remove tax from 21.76 | 8.875% | tax 1.77, price before tax 19.99 |
| Add tax to 0.04 | 5% | tax 0.00 (0.002 rounds to nothing), price after tax 0.04 |
When removing tax gives no exact answer
Because the tax is rounded to the cent, some prices after tax cannot be produced by any price before tax. For example, at 20% a price before tax of 0.07 becomes 0.08 and 0.08 becomes 0.10, so no price before tax gives exactly 0.09. The share of such prices is about rate ÷ (100 + rate): around 9% at 10% and about 17% at 20%.
When this happens the tool does not hide it. It shows:
- the closest estimate for the price before tax (the amount you entered minus the rounded tax), clearly marked as not an exact match; and
- the two nearest candidates, one below and one above, with the price after tax that each one recalculates to. That recalculated price is not the amount you entered; the last column shows the difference.
Going the other way is always safe: a price before tax always maps to exactly one price after tax, and two different prices before tax never give the same price after tax. If you start from the price before tax and add tax, there is no ambiguity.
Notes
- The tax rate must be between 0% and 100%. A rate of 0% gives a tax of 0 and the same price before and after tax.
- Amounts can be 0 or more, up to 9,999,999,999.99, with up to 2 decimal places. Use a period as the decimal separator; commas are accepted only as thousands separators.
- Rounding differs between places and businesses. The default is to round to the nearest cent (halves go up). Some invoices round the tax on each line, and some rules round up or down; choose the option that matches the rules you must follow.
- If the tax in your area is a combination of rates (for example a state rate plus a local rate), enter the total rate. The tool does not look up rates or combine them for you.
- This is a general percentage calculator. It does not handle tax filing, exemptions, tax on shipping, reverse-charge VAT, or any country's rules, and the results are for reference only. Check the rate and the rules with the tax authority or your accountant.
- To work out a discount or a percentage change, see the Discount Calculator or the Percentage Change Calculator.
Frequently asked questions
How do I calculate sales tax?
Choose "Add tax to a price", enter the price before tax and the sales tax rate for your location. The tool shows the tax and the total. For a combined state and local rate, enter the total rate (for example 8.875).
How do I get the price before tax from a price that includes VAT?
Choose "Remove tax from a price", enter the price including VAT and the VAT rate. The tax is the price × rate ÷ (100 + rate), not the price × rate.
Why is the tax not the same as price × rate on a tax-inclusive price?
Because the rate applies to the price before tax. For a price of 120.00 at 20%, the tax is 20.00 (120 × 20 ÷ 120), not 24.00.
Which rate should I enter?
The one that applies to what you are buying or selling in your place. This tool does not provide a list of rates, because they change and differ by item and location.