Discount Calculator

How to use the discount calculator

1. Enter the original price and the discount percentage. The result shows what you pay and how much you save.
2. If the store gives a second discount on top, such as an extra 10% off sale items at the till, type it in Extra discount. It is applied to the already-reduced price, which is how most shops apply coupons.
3. Add the sales tax or VAT rate if you want the final total including tax. Tax is applied last, after all discounts.
4. Switch to Find the original price when you only know what you paid and the percentage taken off.

The currency does not matter. The tool works with plain numbers, so you can use dollars, pounds, euros or rupees.

The formulas

Price after discount = original × (1 − discount ÷ 100) Two discounts = original × (1 − d1 ÷ 100) × (1 − d2 ÷ 100) Total with tax = price after discounts × (1 + tax ÷ 100) Original from sale = sale price ÷ (1 − discount ÷ 100)

Notice that the original-price formula divides. A common mistake is to add the discount back on, for example adding 25% to a sale price of 45. That gives 56.25, not the true original of 60, because the 25% was taken from the larger number.

Worked example: stacked discounts and tax

A jacket costs 80. It is marked 25% off, and you have a coupon for an extra 10% off the sale price. Sales tax is 8%.

1. First discount: 80 × (1 − 0.25) = 80 × 0.75 = 60.00
2. Second discount: 60 × (1 − 0.10) = 60 × 0.90 = 54.00
3. Tax: 54 × 1.08 = 58.32

You save 26.00 before tax, which is an effective discount of 32.5%, not 35%. Percentages do not add when they are applied one after the other, because the second one works on a smaller number. If the order were reversed (10% first, then 25%), the result would be the same, since multiplication gives the same answer in any order.

Finding the original price: you paid 45 after a 25% discount. 45 ÷ 0.75 = 60.00, so the original price was 60 and the saving was 15.

Common discount values

Stacking two common offers shows how quickly the effective rate drifts from the headline: 20% then 20% is 36% off, not 40%; 50% then 20% is 60% off, not 70%; and 30% then 30% is 51% off.

Tips for reading sale prices

• “Up to” claims: “up to 70% off” only promises that one item is at 70%, so check the actual price.
• Compare the final price, not the percentage: 30% off an inflated price can cost more than 10% off a fair one.
• Check whether tax is included: in the UK, EU and many other countries the shelf price already includes VAT. In the US it is added at the till.
• Rounding: this tool rounds only the displayed amounts to two decimals, and keeps full precision in between, so the final total can differ by a cent from a till that rounds at every step.

Common mistakes

• Adding percentages together. Two successive discounts of 30% and 20% are 44% off (0.7 × 0.8 = 0.56), not 50%.
• Taking a percentage off the wrong number. If a price rose by 25% and then fell by 25%, you are not back where you started: 100 × 1.25 × 0.75 = 93.75.
• Reversing a discount by adding it back. To undo 20% off, divide by 0.8 (add 25%), not 1.2.
• Mixing up the discount rate and the payment rate. 35% off means you pay 65%, so the multiplier is 0.65. The table above lists the multiplier for the common offers.
• Forgetting that tax applies to the reduced price. In most places tax is charged on the amount after discounts, so a larger discount also reduces the tax you pay.

Accuracy and limits

The calculator handles percentages from 0 to 100 and any non-negative price. It does not know about minimum spends, buy-one-get-one offers, shipping fees or per-item caps, so apply those by hand. Where a retailer rounds each line item or each tax separately, a receipt can differ by a few cents.

Frequently asked questions