RunToolRunDiscount Calculator
Calculate discounted prices.
How to Calculate a Discount
Enter the original price
Type the price before the discount.
Enter the discount percentage
Add the advertised percentage — 20%, 50%, whatever the tag says.
See what you pay and save
The final price and the money saved appear instantly.
Stacked discounts multiply, they do not add
Fifty percent off, then a further twenty percent off, is not seventy percent off. The second discount applies to the already-reduced price, so you pay 0.5 × 0.8 = 0.4 of the original — a 60% total reduction, not 70%.
This is arithmetic rather than a retailer's trick, but it is arithmetic that consistently favours the seller in how the offer sounds. Whenever two discounts are combined, multiply what remains rather than adding what is taken off.
The order of discount and tax
Whether a discount is applied before or after tax changes the final figure. Applied before, the tax is calculated on the reduced price and you save on the tax too. Applied after, you pay tax on the full price and the discount comes off the total.
Which one applies depends on jurisdiction and on the type of discount — a manufacturer's coupon is often treated differently from a store discount. If a receipt total does not match your expectation, this is usually the reason rather than an error.
Working out the real percentage
Retail offers are frequently expressed in forms that obscure the actual reduction. 'Buy one get one free' is 50% off if you want two items and nothing at all if you want one. 'Three for the price of two' is a third off, or 33.3%. 'Buy two get one half price' is 16.7% off.
Converting every offer to a single percentage of the total you will actually pay is the only way to compare them, and it regularly reverses which deal looks better.
Comparing against a real reference price
A percentage is meaningless without a trustworthy starting price. Reference prices are sometimes raised ahead of a sale, and several jurisdictions now require the advertised 'was' price to be one at which the item was genuinely sold for a defined period, precisely because of this.
The practical defence is to compare the final price against other sellers rather than against the claimed discount. Forty percent off an inflated price can be more expensive than ten percent off an honest one.
Margin and markup are not the same
For anyone pricing rather than buying, this is the equivalent trap. A 50% markup on cost gives a 33% margin on the selling price, not 50%. Confusing the two systematically overstates profitability, and the error grows with the percentage.
The calculation runs in your browser, so cost prices and margins entered here are not transmitted anywhere — relevant if you are working out pricing for your own business rather than shopping.
The amount saved is not the amount gained
A discount only saves money on something you were going to buy anyway. Spending £60 on a £100 item you did not need is not a £40 saving; it is £60 spent. This is obvious stated plainly and completely invisible in the moment, which is what the entire discipline of sale pricing is built on.
The useful discipline is to decide what an item is worth to you before looking at the discount, then compare the final price against that figure rather than against the original. Deals that survive the comparison are genuinely good ones, and there are fewer of them than the percentages suggest.