Discount Calculator
See the real price after a discount, exactly how much you're saving, and what stacked offers like "extra 10% off sale prices" genuinely add up to. Updates as you type.
How sale discounts really work
A discount takes a percentage off the price, so the quick method is to multiply by what's left: 30% off means you pay 70%, i.e. price × 0.70. A £89.99 jacket at 30% off costs £62.99, saving you £27.00.
Why "50% + 20% extra" isn't 70% off
Retailers love stacking offers because they sound bigger than they are. An extra 20% off a half-price item applies to the already reduced price, not the original. £100 → £50 → £40, which is a 60% total discount, not 70%. The gap gets wider the bigger the numbers: 50% + 50% extra is 75% off, not free. Our calculator has a dedicated field for the stacked offer so you can see the honest, effective percentage before you get to the till.
A £249 pair of headphones is listed at "40% off, plus an extra 15% with code". First cut: £249 × 0.60 = £149.40. Second cut: £149.40 × 0.85 = £126.99. Total saving £122.01 - an effective discount of 49%, not the 55% the banner implied.
Is it actually a bargain?
A percentage off is only meaningful if the "original" price was real. UK retailers have been pulled up repeatedly by the Competition and Markets Authority for inflating the reference price shortly before a sale. Two quick checks: search the product's price history on a tracker site, and compare against what other shops charge today. A genuine 20% off a fair price beats a theatrical 60% off an invented one.
One more thing worth knowing at the till: UK shelf prices already include VAT, so the discount applies to the VAT-inclusive figure - no need to adjust for tax the way US shoppers do. If you ever need to pull the tax out of a discounted price for expenses, that's a job for the reverse VAT calculator, and for any other quick sums there's the general percentage calculator.
Frequently asked questions
How do I calculate a discount percentage off a price?
Multiply the price by (1 minus the discount as a decimal). For 25% off £80: £80 × 0.75 = £60. The amount saved is the original minus the sale price - £20 here.
How do stacked or double discounts work?
The second percentage applies to the already-discounted price, so the totals multiply: 30% off followed by an extra 10% off leaves you paying 0.70 × 0.90 = 63% of the original, a 37% effective discount rather than 40%.
How do I work out the original price from a sale price?
Divide the sale price by (1 minus the discount as a decimal). If something costs £42 after 30% off, the original was £42 ÷ 0.70 = £60.
What's the fastest mental shortcut for discounts?
Work from 10%: shift the decimal point one place. For 30% off £45, 10% is £4.50, so the discount is £13.50 and you pay £31.50. For 25%, halve and halve again.