How the discount calculator works
Choose what you want to find. Sale price takes a percentage off the original price and shows how much you save. What % off it is compares an original and a reduced price, which is handy for checking whether a "huge saving" is really that big. Original price works backwards from a sale price and the percentage off. You can also add a second discount on top, for offers like "extra 10% off sale items".
How to work out a percentage off
Sale price = original price × (1 − discount % ÷ 100)
So 25% off £80 is a saving of £80 × 0.25 = £20, and the sale price is £80 × 0.75 = £60. A quick way to do it in your head: 10% is the price divided by 10, so 10% of £80 is £8, 20% is £16 and 5% is £4. Add them up to get 25%.
Common discounts on a £50 item
| Discount | Multiply by | You save | You pay |
|---|---|---|---|
| 10% off | 0.9 | £5 | £45 |
| 15% off | 0.85 | £7.50 | £42.50 |
| 20% off | 0.8 | £10 | £40 |
| 25% off | 0.75 | £12.50 | £37.50 |
| 30% off | 0.7 | £15 | £35 |
| 40% off | 0.6 | £20 | £30 |
| 50% off | 0.5 | £25 | £25 |
What percentage off is this?
If a shop shows the old and new prices but not the percentage, divide the saving by the original price:
A coat reduced from £120 to £90 saves £30, and 30 ÷ 120 × 100 = 25% off. Always divide by the original price, not the sale price. Dividing by £90 would give 33.33%, which overstates the deal.
How to find the original price before a discount
Divide the sale price by one minus the discount as a decimal. If something costs £54 after 10% off, the original price was £54 ÷ 0.9 = £60. Adding 10% back on to £54 gives £59.40, which is wrong, because the 10% was taken from the bigger original price.
Stacked discounts: why 25% plus 10% isn't 35%
When a second discount is applied to an already reduced price, the percentages don't simply add together. Take £80 with 25% off (£60), then an extra 10% off: you pay £60 × 0.9 = £54. That's a total saving of £26, or 32.5% off the original price, not 35%.
The order doesn't matter: 10% then 25% gives the same £54. But "35% off" and "25% plus an extra 10%" are different deals, so the single bigger discount is better for you.
Tips for spotting a genuine deal
- Check the "was" price: misleading price claims are banned as unfair commercial practices under the Digital Markets, Competition and Consumers Act 2024, whose consumer rules came into force on 6 April 2025. It still pays to check what the item has really sold for recently.
- Compare the final price: a 30% discount at one shop can still cost more than a 20% discount at another if the starting prices differ.
- Watch delivery costs: a £5 delivery charge on a £20 saving cuts it by a quarter. Fees you can't avoid should now be included in the headline price, but optional delivery upgrades won't be.
For other percentage sums, use the percentage calculator. If you sell products and want to know how a sale will affect your profit, try the profit margin calculator.
Frequently asked questions
How do I calculate 20% off a price?
Multiply the price by 0.8. For example, 20% off £45 is £45 × 0.8 = £36, a saving of £9.
How do I work out what percentage off something is?
Take the sale price away from the original price, divide by the original price and multiply by 100. A drop from £75 to £60 is 15 ÷ 75 × 100 = 20% off.
Is 20% off and then another 20% off the same as 40% off?
No. Two 20% discounts multiply to 0.8 × 0.8 = 0.64, so you pay 64% of the price, which is 36% off in total rather than 40%.
How do I find the original price from the sale price?
Divide the sale price by 1 minus the discount as a decimal. If a £36 item is 40% off, the original price was £36 ÷ 0.6 = £60.
How much is 30% off £60?
30% off £60 is a saving of £18, so you pay £42.
Last reviewed October 2026 using 2026/27 figures. This calculator gives an estimate for guidance only.