Discount Calculator: Work Out the Sale Price and What You Save

Quick answer

To calculate a discount: multiply the price by the discount percentage and take it off. 25% off £80 = 80 × 0.25 = £20 off, so you pay £60. For stacked discounts, apply them one after another, not added together.

Use the discount calculator above

Enter the original (full) price and the percentage discount in the tool above. It returns the amount you save and the final sale price instantly. Change either figure and the result updates, so you can compare a 20% off code against a fixed £5 voucher in a few seconds.

How the discount maths works

A percentage discount is just a slice of the original price taken off. The method never changes, whatever you are buying:

• Saving = original price × (discount % ÷ 100)
• Sale price = original price − saving

There is a quicker one-step version that gives the sale price directly. Multiply the original price by what is left after the discount:

• Sale price = original price × (1 − discount % ÷ 100)

So a 30% discount means you pay 70% of the ticket price, because 100% − 30% = 70%, and 70% as a decimal is 0.70. A £80 coat at 30% off costs 80 × 0.70 = £56. The same logic runs in reverse: if you know the sale price and the original price, the discount percentage is (saving ÷ original price) × 100. A jacket cut from £120 to £90 has a £30 saving, and 30 ÷ 120 = 0.25, so that is 25% off.

Most UK shop prices already include VAT at the standard 20% rate, so the discount comes off the VAT-inclusive figure you see on the label. You do not need to strip VAT out first. If you are a business pricing goods before tax, work out the discount on the net price and add VAT afterwards - our VAT calculator handles that part.

Worked examples with the numbers shown

Example 1 - a single percentage off. Priya spots a £245 winter coat with 35% off in the January sale. Saving = 245 × 0.35 = £85.75. Sale price = 245 − 85.75 = £159.25. She pays £159.25 and keeps £85.75. Doing it the one-step way gives the same answer: 245 × 0.65 = £159.25.

Example 2 - stacked discounts (the trap). An online store advertises “50% off, then an extra 20% off at checkout” on a £200 pair of boots. That is not 70% off. The discounts apply one after the other. First: 200 × 0.50 = £100. Then 20% comes off the £100, not the original £200: 100 × 0.80 = £80. So you pay £80, a real saving of £120, which is 60% off overall - good, but not the 70% it sounds like. To stack discounts, multiply the decimals: 0.50 × 0.80 = 0.40, meaning you pay 40% of the original.

Example 3 - percentage off versus a fixed voucher. Tom has a £45 shopping basket and two offers he cannot combine: 15% off everything, or a flat £8 off. The 15% saves 45 × 0.15 = £6.75. The £8 voucher beats it. The percentage only wins once the basket passes £53.34, because 8 ÷ 0.15 = 53.33. Below that figure, take the cash voucher; above it, take the percentage. A quick way to compare offers like this is to convert everything into pounds saved, which is exactly what a percentage calculator does in the other direction.

Getting the most from a discount

A discount is only worth taking on something you were going to buy anyway. Spending £60 to “save” £40 still costs you £60. With that in mind, here is how to make discounts work harder:

• Check the reference price. A genuine deal compares against the price the item normally sold at, not a brief “high” price set just before the sale. The Chartered Trading Standards Institute pricing guidance and consumer protection rules expect “was” prices to be real recent prices.
• Watch the post-discount unit cost. For groceries and bulk buys, work out the price per item or per 100g after the discount. A multi-buy is not always cheaper than the loose product on offer elsewhere.
• Time the big sales. Black Friday, Boxing Day and end-of-season clearances move the same stock at different prices. If it is not urgent, note the price and wait.
• Factor in delivery. A 20% discount that triggers a £4.99 postage charge can wipe out the saving on a small order. Add postage before you judge the deal.
• Keep it inside a budget. Plan your spending so a sale does not blow a hole in the month. The free MoneyHelper Budget Planner is a solid place to start, or use our budget calculator to map income against outgoings.

If you sell rather than buy, the same tool helps you set an offer that still leaves a profit. Decide the lowest price you can accept, then work back to the discount percentage that lands there. Pair it with our profit margin calculator so a tempting “40% off” promotion does not quietly turn each sale into a loss.

Common mistakes people make with discounts

• Adding stacked percentages together. As Example 2 showed, 50% then 20% is 60% off, not 70%. Sequential discounts always apply to the reduced price, so multiply the decimals rather than adding the percentages.
• Confusing discount with markup. A 25% discount and a 25% markup are different sums because they work off different starting figures. Adding 25% to £80 gives £100, but taking 25% off £100 gives £75 - you do not get back to where you started. If you are adding rather than subtracting, use the markup calculator instead.
• Treating “up to 70% off” as the whole shop. “Up to” means the single best-reduced item. Most of the range will be discounted by far less, so check each tag.
• Ignoring whether it is a need or a want. The biggest saving is not buying the thing at all. A discount on an impulse purchase is still money spent.
• Rounding too early. Round only the final answer. Rounding mid-calculation, especially on stacked or VAT-inclusive prices, can throw the pennies out.

These figures are estimates for guidance only and are not personal tax or financial advice. Always check the final price at the till or checkout before you pay.

Related calculators

Once you have the sale price, line up the rest of your sums. Use the tip calculator when you are splitting a restaurant bill, the percentage calculator for any other “what percent of” question, and the VAT calculator if you need to add or remove the 20% standard rate from a price.

Discount maths that stores rely on you getting wrong

Comparing per-unit prices beats any sticker: our percentage calculator does the division, and the budget calculator shows what the saving means monthly.