How to calculate sales tax

Sales tax is a percentage added to a price, and the arithmetic is one multiplication. Here is how to add it to a price, how to remove it from a total to find the pre-tax amount, why you cannot just subtract the percentage, and how sales tax differs from VAT and GST.

By the Calculator Den team · Updated 2026-11-04

Sales tax is a percentage added to the price of something, and working it out takes one short step. The part people get wrong is not adding it, but taking it back off a total, where you cannot simply subtract the percentage. This guide shows how to add sales tax to a price, how to remove it from a tax-inclusive total to find the pre-tax amount, how prices are shown tax-exclusive in the US and tax-inclusive in most of the world, and how sales tax differs from VAT and GST. The numbers are currency-neutral, and rates vary widely by place, so use your own local rate: the method does not change.

How to add sales tax to a price

To add sales tax, multiply the price by the tax rate to get the tax amount, then add it on. Or do it in one step by multiplying by one plus the rate.

Tax amount = price × (rate ÷ 100)

Total = price × (1 + rate ÷ 100)

Worked example: a 50 item at 8% sales tax. The tax is 50 × 0.08 = 4, so the total is 50 + 4 = 54. The one-step version: 50 × 1.08 = 54. Another: 80 at 10% is 80 × 1.10 = 88, with 8 of tax. The quick mental check for 10% is to move the decimal one place (10% of 80 is 8) and add it on.

How to remove sales tax from a total (reverse sales tax)

This is where the mistakes happen. If you have a tax-inclusive total and want the pre-tax price, you cannot subtract the tax percentage, because the tax was added to the smaller pre-tax amount, not the bigger total. Instead, divide by one plus the rate.

Pre-tax price = total ÷ (1 + rate ÷ 100)

If a total is 54 including 8% tax, the pre-tax price is 54 ÷ 1.08 = 50, and the tax portion is 54 − 50 = 4. The wrong way, subtracting 8% from 54, gives 54 − 4.32 = 49.68, which is 0.32 too low, because 8% of 54 is bigger than 8% of 50. This reverse calculation is exactly what you need to pull the tax out of a receipt total, or to work out the net figure for bookkeeping from a gross one.

If you only want the tax portion of an inclusive total, there is a direct shortcut: tax = total × rate ÷ (100 + rate). For a 54 total at 8%, that is 54 × 8 ÷ 108 = 4, matching the figure above. And if you know the before and after prices but not the rate, the rate is (total − pre-tax) ÷ pre-tax: a price that went from 50 to 53.50 was taxed at 3.50 ÷ 50 = 7%.

More sales tax examples (add and remove)

• Add 15% to 200. 200 × 1.15 = 230, with 30 of tax.
• Remove 15% from a 230 total. 230 ÷ 1.15 = 200, so the tax was 30.
• Add 7.25% to 48. 48 × 1.0725 = 51.48, with 3.48 of tax (rounded to the nearest cent).

Rounding is usually to the nearest cent after multiplying, and some tills round each line while others round the total, so a receipt can differ by a cent from a single calculation. Neither is wrong; the rounding rule is set by the seller or local law.

Sales tax on a discounted price

When an item is both discounted and taxed, the usual order is that the discount comes off first and tax is charged on the reduced price. Take a 120 item with 25% off and 8% sales tax: the discount gives 120 × 0.75 = 90, then tax gives 90 × 1.08 = 97.20, with 7.20 of tax. For a percentage discount the order does not actually change the total, because 120 × 0.75 × 1.08 is the same as 120 × 1.08 × 0.75. The order only changes things with a flat-amount coupon, or a manufacturer coupon that some places tax before deducting, so the receipt is the final word on which applies.

Sales tax: tax-exclusive versus tax-inclusive prices

Where the tax sits in the shown price is the big regional difference. In the United States and Canada, shelf and online prices are usually tax-exclusive: the price you see is before sales tax, and the tax is added at the register, so the amount you pay is higher than the sticker. In most other countries, consumer prices are tax-inclusive: the VAT or GST is already baked into the shelf price, so the sticker is what you pay. This is why a US total surprises visitors and why, where prices are inclusive, you usually need the reverse calculation above to find how much of a price is tax.

Sales tax versus VAT and GST

They end up as a percentage on what you buy, but they work differently behind the scenes. A US-style sales tax is charged once, at the final retail sale to the consumer. VAT (value-added tax) and GST (goods and services tax), used across the UK, the EU, South Africa, Botswana, India, Australia and many other countries, are charged at each stage of the supply chain, with businesses reclaiming the tax they paid, so only the final consumer bears the full amount. For a shopper the maths of adding or removing the percentage is identical; the difference matters mainly to businesses that register for the tax and file returns. Our guide on what VAT is covers that side in plain terms.

Combined sales tax rates (state plus local)

In many places the rate you pay is several rates stacked together, for example a state rate plus a county or city rate in the US. These are added, not compounded: a 6% state rate and a 2% city rate make an 8% combined rate, which you then apply once, not a 6% tax that is then taxed again at 2%. So find your total combined rate first, then do a single calculation with it. Because local rates change and vary street by street, always use your current local rate rather than a remembered one.

Common sales tax mistakes

• Subtracting the percentage to remove tax. From a 54 total at 8%, the pre-tax price is 54 ÷ 1.08 = 50, not 54 − 8%. Divide by one plus the rate.
• Using a tax-inclusive price as if it were pre-tax. Where shelf prices already include the tax, adding tax again double-counts it.
• Compounding combined rates. A 6% and a 2% local rate make 8% applied once, not stacked multiplicatively.
• Not knowing whether tax comes before or after a coupon. A percentage discount gives the same total in either order, but a flat coupon taken off after tax can leave you paying tax on the full price, so check the receipt (and our discount calculator for the markdown itself).

Add tax by multiplying by one plus the rate, and remove it by dividing by one plus the rate. When you want it instant, the free VAT and sales tax calculator adds or removes tax at any rate, the discount calculator handles the markdown that often comes first, and the percentage calculator covers the wider percentage questions.