The short answer

To work out a discount, multiply the original price by the percentage off and divide by 100. That gives you the amount you save. Subtract it from the original price and you have the sale price. For example, 25% off $80 is 80 × 25 ÷ 100 = $20 off, so you pay $60.

If you would rather skip the maths, this percentage discount calculator does all of it for you — the discount amount, the sale price, the real percentage off, and stacked discounts too. The rest of this guide shows you how the numbers work, so you can check any price tag in your head.

How to calculate a discount in three steps

Every discount question comes down to the same three steps. Once you know them, you can work out any sale price without a calculator.

Step 1: Find the discount amount. Multiply the original price by the percentage off, then divide by 100. On a $120 jacket at 30% off, that is 120 × 30 ÷ 100 = $36.

Step 2: Find the sale price. Subtract the discount from the original price. The jacket costs 120 − 36 = $84.

Step 3: Check your saving. The discount amount from Step 1 is what you keep in your pocket — $36 in this case.

A quicker way to get the sale price in one move: pay 100% minus the discount. At 30% off you pay 70%, so 120 × 70 ÷ 100 = $84. Same answer, one step.

Worked examples

25% off $80. Discount: 80 × 25 ÷ 100 = $20. You pay $60 and save $20.

15% off $59.99. Discount: 59.99 × 15 ÷ 100 = $9.00 (rounded). You pay about $50.99 and save about $9.00.

40% off £250. Discount: 250 × 40 ÷ 100 = £100. You pay £150 and save £100.

10% off $45. Discount: 45 × 10 ÷ 100 = $4.50. You pay $40.50.

Notice the pattern: 10% of any price is just the price with the decimal point moved one place left. That is the easiest discount to work out in your head, and it is the key to estimating the rest — 20% is double 10%, 30% is triple, and 5% is half of 10%.

How to find what percentage off a sale price is

Sometimes the shop shows you two prices and no percentage. A jacket was £120 and is now £84 — what percentage off is that?

Subtract the sale price from the original price, divide by the original price, then multiply by 100. Here that is (120 − 84) ÷ 120 × 100 = 30% off. The same formula works for any "was / now" price tag, and it is how you check whether a claimed discount is real.

A quick sense-check: if the sale price is half the original, that is 50% off. If it is three-quarters of the original, that is 25% off. If it is nine-tenths, that is 10% off.

Stacked discounts: 20% off plus an extra 10% is not 30% off

This is where shoppers — and sometimes shop signs — get it wrong. When a second discount applies after the first, it comes off the already-reduced price, not the original.

Take a $100 item at 20% off, plus an extra 10% at checkout. The first discount takes it to $80. The extra 10% comes off $80, not $100, so it takes off $8. You pay $72, and the real total discount is 28%, not 30%.

The gap grows with bigger numbers. 50% off plus another 50% off is not free — it is 75% off. The first half takes $100 to $50, the second half takes $50 to $25. Three stacked discounts of 20%, 10% and 5% come to 31.6% off in total, not 35%.

If you ever see "extra 10% off sale items", work it out in this order: apply the first discount, then the second to the new price. Or use the percentage discount calculator and enter up to three discounts — it shows the true total percentage and the final price.

Fixed amount off: "$15 off $60"

Not every deal is a percentage. A "$15 off $60" coupon is a fixed amount, and its percentage depends on the price. On a $60 item, $15 off is 25% off (15 ÷ 60 × 100). On a $150 item, the same $15 coupon is only 10% off. A fixed-amount coupon is always worth more, in percentage terms, on a cheaper item — which is why shops set minimum spends on them.

Common discounts at a glance

For a quick check before you shop: 10% off $50 is $45; 20% off $80 is $64; 25% off $100 is $75; 30% off $120 is $84; 50% off anything is half price. If the tag price is close to one of these, you can spot a wrong "discount" in seconds.

Mistakes to watch for

Adding stacked percentages. As above, 20% + 10% is 28%, not 30%. Always apply discounts one after another.

Forgetting tax. A discount comes off the price before tax in most places, so the tax is charged on the reduced price. A $100 item at 20% off costs $80 before tax, and the tax is worked out on $80.

Comparing against the wrong "was" price. A discount is only as honest as the original price it is measured from. If the "was" price was inflated for a week before the sale, the real saving is smaller than the tag claims. Work out the percentage from a price you trust, not from the crossed-out number.

Rounding. Shops round to the nearest cent or penny, so your hand calculation may differ by a cent from the till. That is normal, not a mistake.

When to use a calculator instead

Mental maths is fine for one discount on a round number. For stacked discounts, odd prices like $59.99, or a fixed amount you want as a percentage, a calculator is faster and exact. The free percentage discount calculator runs in your browser with no signup: enter the price and the discount, and it shows the discount amount, the sale price and what you save — including stacked discounts of up to three levels.