Discount calculator
Type a price and the % off to see the sale price and how much you save. The answer updates as you type.
Extra % off the sale price
For deals like "take an extra 10% off sale prices". Uses the price and % off above.
Multi-buy deal as a % off
Turn "buy X get Y free" into a % off, so you can compare it with other deals. A 3 for 2 is buy 2 get 1 free.
Work backwards
Find the original price from a sale price, or the % off from two prices.
How this calculator works
A percentage discount takes that share of the price off. To work out the sale price, the calculator multiplies the price by what's left after the discount:
- Sale price = price × (1 − % off ÷ 100). For example, 25% off £40 is £40 × 0.75 = £30.
- Amount saved = price − sale price. In the example, that's £10.
Stacked discounts are applied one after the other, so the second discount comes off the already reduced price: final price = price × (1 − first % ÷ 100) × (1 − extra % ÷ 100). That's why 20% off and then an extra 10% off is 0.8 × 0.9 = 0.72 of the price, which is 28% off in total, not 30%.
Multi-buy deals give you some items free, so the % off across everything you take home is: free items ÷ (items paid for + free items) × 100. Buy 2 get 1 free (3 for 2) is 1 ÷ 3, or 33.33% off. Buy one get one free is 50% off.
Working backwards reverses the sums. Original price = sale price ÷ (1 − % off ÷ 100), so £30 after 25% off was £30 ÷ 0.75 = £40. The % off = (original − sale price) ÷ original × 100.
Prices are rounded to the nearest penny, as shops do. Tills sometimes round each item separately, so a total can be a penny or two different.
Tips for checking a deal
- Check the "was" price is real. UK consumer law says reference prices like "was £50, now £25" mustn't mislead you, but some are inflated. If you can, look up what the item sold for over the last few weeks, or compare it with other shops.
- Stacked discounts don't add up. "Extra 10% off sale prices" on top of 20% off is 28% off, not 30%. Use the extra discount box to see the real figure.
- Compare multi-buys with a straight discount. A 3 for 2 is 33% off, but only if you'd use all three. If you only need one, a 20% off deal on a single item saves you more.
- "Up to 70% off" usually means only a few items. Check the discount on the thing you actually want.
- Compare unit prices. On food and toiletries, the price per 100g or per item on the shelf label is often a better guide than the discount.
- It's only a saving if you'd buy it anyway. Spending £30 on something you didn't need isn't saving £10.
Frequently asked questions
How do I work out a discount in my head?
Start with 10%: move the decimal point one place left, so 10% of £45 is £4.50. Double it for 20% (£9), halve it for 5% (£2.25), and add those up for other amounts, like 15% = 10% + 5% (£6.75). Half price is 50%, and a quarter off is 25%.
Is 20% off and then another 10% off the same as 30% off?
No. The extra 10% comes off the price that's already been reduced, so you pay 80% × 90% = 72% of the original price. That's 28% off in total. On a £100 item, you'd pay £72 rather than £70.
Is a 3 for 2 deal better than 30% off?
A 3 for 2 is the same as 33.33% off each item, so it's slightly better than 30% off, but only if you want all three. "Half price on the second item" is 25% off across the two items.
How do I find the original price from a sale price?
Divide the sale price by what's left after the discount. If something costs £36 after 40% off, you're paying 60% of the price, so the original was £36 ÷ 0.6 = £60. Use the "Work backwards" box to do this for you.
Can I save this calculator to my phone's home screen?
Yes. On an iPhone, open this page in Safari, tap the Share button, then "Add to Home Screen". On Android, open it in Chrome, tap the menu (three dots), then "Add to Home screen" or "Install app". It then opens like an app. The page is small, so it loads quickly even on a weak signal in a shop.
Does it work with VAT?
Shop prices for consumers in the UK include VAT, so the discount comes off the price you see and the sale price already includes VAT. For prices shown without VAT, try our other money tools.
Is this financial advice?
No. It's a simple calculator to help you check the maths on a deal. It isn't a recommendation to buy anything.
Results are estimates for illustration only and aren't financial advice. Prices are rounded to the nearest penny, so a shop's till may differ by a penny or two.