Discount Calculator: Percent Off & Sale Price
Three questions in one place: what a discount leaves you paying, what percentage off a sale price actually represents, and what a price was before the reduction. The stacking field is the interesting one, because two discounts never add up the way the sign implies.
The price before anything is taken off.
The percentage on the sign.
For "extra 20% off sale prices". Applied after the first.
Think in what survives, not in what is removed
A discount is easier to handle if you flip it. Thirty percent off does not mean "subtract 30"; it means seventy percent of the price remains. Multiply by 0.70 and you are done in one step, with no subtraction to get backwards.
That framing pays off immediately when discounts stack.
Stacked discounts never add up
"30% off, plus an extra 20% off sale prices" is not 50% off. The second discount is taken from the already-reduced price, so it is worth less than it looks. Multiply the survivors: 0.70 × 0.80 = 0.56, which means 44% off. On a 120 item that is 67.20, not the 60 the signage implies.
The gap widens as the numbers get bigger. Two 50% discounts stacked give 75% off, not 100% — the item never becomes free, however many percentage discounts you pile on. Anything short of a single 100% always leaves something to pay.
For pure percentages the order does not matter, because multiplication does not care. Order does matter the moment a fixed amount is involved. On a 100 item, "10 off, then 20% off" gives 72. "20% off, then 10 off" gives 70. If a retailer gets to choose the order, they will choose the first one. If you have a voucher and a sale, it is worth asking which is applied first.
Multibuys as percentages
Offers that are not expressed as percentages usually are one underneath, as long as you actually want all the items:
- Three for two — one free item in three, so 33.3% off.
- Buy one get one free — 50% off, if you needed two.
- Buy one get one half price — 25% off across the pair.
- Buy two get one half price — 16.7% off across the three.
The qualifier matters. A three-for-two on something you would have bought once is a 50% price increase dressed as a saving.
Percent off is not the same as margin
A markup and a margin are calculated against different bases and people mix them up constantly. Buy at 100, sell at 150: that is a 50% markup on cost and a 33.3% margin on the selling price. Discount that 150 by 20% and the margin does not fall by 20 points — it falls to 16.7%, less than half what it was. Retail discounting eats margin much faster than it looks, which is why a 30% sale is a bigger decision than a 30% sign suggests.
What the "was" price is worth
A percentage off is only meaningful if the higher price was real. In the EU, the Omnibus Directive requires that any announced price reduction states the lowest price the seller applied in the previous 30 days, precisely because a reference price that nobody ever paid makes the discount fictional. Similar rules exist elsewhere. If a product has been "40% off" for six months, the sale price is the price.
Where this tool falls short
- Tax is not handled. In VAT countries the shelf price already includes tax, so the discount applies to the gross figure and the percentage holds. In the US, sales tax is added after the discount at the till, so what you actually hand over is more than the number here. Strip or add tax with the VAT calculator if you need the invoice figure.
- Only two discounts stack. Loyalty points, cashback and shipping thresholds are not percentages of the item price and do not belong in the same multiplication.
- Retailer rounding varies. Some round the discount down, some round the final price down, some round to the nearest 0.05 where small coins have been withdrawn. This tool rounds the final price to two decimals, half away from zero. Expect the till to disagree by a cent occasionally.
- Number parsing has one blind spot. Both
1,234.56and1.234,56are read correctly, but a lone comma with exactly three digits after it is always taken as a thousands separator, so1,500means fifteen hundred. Type1.5if you meant one and a half.
Everything runs in this tab. No prices are uploaded, logged or stored anywhere.
Frequently asked questions
How do I calculate a percentage off a price?
Multiply by what remains rather than subtracting. For 30% off, multiply the price by 0.70. For 15% off, multiply by 0.85. One step, and no chance of subtracting from the wrong number.
Is 30% off plus an extra 20% off the same as 50% off?
No. The second discount comes off the already-reduced price, so you keep 0.70 × 0.80 = 0.56 of the original. That is 44% off, not 50%. The gap is six points, and it widens with larger discounts.
How do I find the original price from a sale price?
Divide by what remains. A price of 84 after 30% off was 84 ÷ 0.70 = 120. Adding 30% back to 84 gives 109.20, which is wrong — the discount was taken from the larger number.
Does the order of two discounts matter?
Not for two percentages, because multiplication is commutative. It matters a great deal when one is a fixed amount: on a 100 item, 10 off then 20% off gives 72, while 20% off then 10 off gives 70.
Does this include sales tax or VAT?
No. In VAT countries the shelf price already includes tax so the percentage still holds. In the US, sales tax is added after the discount, so the till total will be higher than the figure shown here.
Last updated September 19, 2026