Discount Calculator
Work out a sale price and how much you save.
What you provide
Result
Final price: 80
The saving is the percentage of the original price; the final price is what remains.
- Final price
- 80
- You save
- 20
What this cannot tell you
- Pure arithmetic on the values you enter.
Take this with you
How this calculation works
The saving is the discount percentage of the original price; the final price is what is left after subtracting it.
What the results mean
- You save
- The cash amount taken off — the discount percentage applied to the original price.
- Stacked discounts
- Two successive reductions multiply rather than add: 20% off then 10% off is 28% off in total, never 30%, because the second applies to the already-reduced price.
Common problems and fixes
- Two discounts do not add up to what I expected
- They multiply. Taking 20% off and then a further 10% leaves 0.8 × 0.9 = 0.72 of the original, so 28% off rather than 30%. Retailers advertise these as "extra 10% off sale prices" for exactly this reason, and the gap widens as the percentages grow.
- I know the sale price and want to find the original
- Divide rather than subtract. If 30% was taken off, the sale price is 70% of the original, so the original is the sale price divided by 0.7. Adding 30% back to the sale price gives a different and wrong answer, for the same reason removing tax is not subtraction.
- The discount needs to come off after tax, not before
- The order changes the total, so follow whichever the seller applies. A discount before tax reduces the taxable amount and therefore the tax; a discount after tax does not. For consumer prices quoted inclusive of tax the distinction usually disappears, but for business invoices it is a real difference.
Frequently asked questions
How do I calculate a percentage off?
Multiply the price by the percentage divided by 100 to get the saving, then subtract it. A 20% discount on 100 saves 20, leaving 80.
How do I work out the percentage discount from two prices?
Take the saving — the original minus the sale price — and divide it by the original, then multiply by 100. An item reduced from 80 to 60 has saved 20, and 20 divided by 80 is 25%. Dividing by the sale price instead gives 33%, which is the markup and a common way to overstate a discount.
Is a bigger percentage always the better deal?
Only at the same starting price, which is why comparing percentages across products misleads. 40% off an inflated price can leave you paying more than 20% off a fair one, and reference prices are not always what anyone charged recently. Compare the final amounts you would actually pay.
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