Three calculators people actually need โ€” a percentage, a sale price, and a price with tax on or off

How to use it

  1. Pick a tab at the top: Percentage, Discount or Tax / VAT. The Percentage tab opens first.
  2. On the Percentage tab there are three separate rows โ€” "what is A% of B", "A is what % of B" and "percentage change from โ†’ to". Fill in only the row you need and the answer appears under it.
  3. On the Discount tab enter the original price and the discount. If you have a second coupon, put it in Extra discount % (stacked). The table shows how much you save, the effective discount in brackets and the sale price.
  4. On the Tax tab choose a rate โ€” 20% (UK VAT), 10%, 8.25% or 0% โ€” then type either the price before tax or the price with tax. The other field and the tax amount fill in as you type, and the hint line tells you which direction is being calculated.
  5. Press Copy result to put the last calculation on your clipboard as one line of text.

Amounts are shown as plain numbers to two decimal places with no currency sign, so the same tool works for dollars, pounds, euros or anything else. Nothing you type is stored or sent anywhere.

The three percentage questions

Almost every percentage problem is one of three, and the confusion is always about which number goes on the bottom. What is 15% of 300? is multiplication (45). 45 is what percent of 300? is division (15%). Percentage change from 300 to 345? is the difference over the starting value (15% increase).

That last one trips people up in a specific way: going 100 โ†’ 150 is a 50% increase, but coming back 150 โ†’ 100 is not a 50% decrease โ€” it is 33.3%. The starting value is always the denominator, and it changed.

Stacked discounts do not add up

30% off plus an extra 20% coupon is not 50% off. The second discount applies to the already-reduced price, so you actually pay 0.7 ร— 0.8 = 0.56 of the original โ€” a 44% discount. On a $100 item that is $56, not $50. Retailers rely on this reading better than it is.

30% then 20%44% off in total
50% then 20%60% off in total
20% then 20%36% off in total

Adding tax vs. removing it

Adding tax is a multiplication: at 20% VAT, ยฃ100 before tax becomes ยฃ120. Removing it is not subtracting 20%, which would give ยฃ96 โ€” you divide by 1.20 to get ยฃ100. The rate always applies to the pre-tax price, so the tax portion of a ยฃ120 total is ยฃ20, which is 16.7% of the total but 20% of the base.

Sales tax and VAT: why the four rates

In the United States shelf prices exclude sales tax, which is added at the register at a rate set by the state and often the city or county โ€” 8.25% is a common combined state-plus-local rate, which is why it has its own button. In the UK and most of Europe the shelf price already includes VAT, so businesses more often need to strip the tax out of a gross figure; the UK standard rate is 20%. Japan, Korea and Australia all use a flat 10% consumption tax or GST, covered by the 10% button. The 0% button is for exempt or zero-rated goods and simply shows the same number in both fields.

Rounding is to the cent, half up. When you start from the tax-inclusive price, the calculator rounds the tax first and takes the net as total minus tax, so the two parts always add back to exactly the total you typed. A $120.00 total at 20% gives $20.00 tax and $100.00 net; a $49.99 item at 8.25% gives $4.12 tax and $54.11 in total.

Frequently asked questions

My receipt shows a slightly different tax amount

Stores usually calculate tax per line item and round each one, while this calculator works on the single figure you enter. Across a long receipt those per-line roundings can differ from a single calculation by a few cents. Neither is wrong; the receipt is what you actually paid.

Can I use a rate that is not on the buttons, like 5% or 13%?

The Tax tab only offers 20%, 10%, 8.25% and 0%. For any other rate switch to the Percentage tab: "what is 13% of 200" gives you the tax to add. To remove an unlisted rate, divide the gross price by 1 plus the rate (for 13%, by 1.13) โ€” the Percentage tab does not do that step for you.

Does the order of two stacked discounts matter?

No. The sale price is the original ร— (1 โˆ’ first discount) ร— (1 โˆ’ second discount), and multiplication is the same in either order. 30% then 20% and 20% then 30% both come to 44% off.

Why does a field I typed in keep changing?

The pre-tax and with-tax fields are linked. Whichever one you edited last is treated as the source and the other is recalculated from it, including when you switch the tax rate. If you want the total to be the fixed number, type it last.

How precise are the percentage answers?

"A% of B" is shown to four decimal places, and percentages (both "A is what % of B" and percentage change) to two. Currency-style results on the other tabs use two decimals.

Related tools