How to use the Discount Calculator
- Enter the original price and the discount percentage.
- Add a second discount if one applies at the till.
- Read the final price and the total saved.
- Use the reverse mode when you know the sale price and want the original.
How the calculation works
A single discount multiplies the price by (1 − rate). Two discounts multiply in sequence rather than adding: 30% off then a further 20% leaves 0.70 × 0.80 = 0.56 of the original, a 44% total reduction rather than 50%. That order does not matter to the result, but the misconception that percentages add is what makes stacked offers look better than they are.
Reversing a discount requires division, not subtraction. If a jacket cost 63 after 30% off, the original was 63 / 0.70 = 90 — subtracting 30% of 63 would wrongly suggest 81.90. The same logic strips tax or markup from a gross figure.
Sale = original × (1 − d₁) × (1 − d₂) ; Original = sale / (1 − d)Source: Proportional arithmetic; multiplicative treatment of successive percentage reductions.
Worked example
A 249 coat is advertised at 35% off, with an extra 15% off for members at the till.
- After the first discount: 249 × 0.65 = 161.85.
- After the member discount: 161.85 × 0.85 = 137.57.
- Total saved = 249 − 137.57 = 111.43.
Final price 137.57, a saving of 111.43 — an effective 44.75% off, not the 50% that adding the percentages suggests.
Frequently asked questions
Do two discounts add together?+
No, they multiply. 20% then 20% is 36% off in total, because the second reduction applies to the already-reduced price.
How do I find the original price from a sale price?+
Divide the sale price by one minus the discount as a decimal. At 40% off, an item costing 72 was originally 72 / 0.60 = 120.
Is 'buy one get one free' the same as 50% off?+
Only if you wanted two. Per item it is 50% off, but it forces the larger purchase, so compare it against the single-item price you actually need.
Is the discount applied before or after tax?+
Almost always before, since tax is charged on the amount you actually pay. That means a discount reduces the tax as well as the price.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.