Discount Calculator

Where a single discount is enough

One discount, one price, one answer: this page is settled maths for the standard sale sticker — 30% off a jacket, 15% off a course fee, 20% off a subscription. It converts what feels like a saving into exact money, which is where the shopping decision really happens: 40.50 off 135 feels abstract; walking out paying 94.50 does not.

Use additional tools when the offer is not single. Two stacked discounts must be applied one after the other (see below — they multiply, they do not add). "Buy one get one half price" is a 25% discount only when the two items cost the same. And a "free gift worth X" needs your honest value judgement, not a calculator. The original price matters too: if a shop quietly raised the pre-sale price a week before, no arithmetic can rescue the deal — that is a data question, and price-tracking history is the antidote.

A worked example, step by step

Problem: a jacket costs 135 with 30% off today; the till adds a loyalty extra of 10% more off. What do you really pay?

1. First discount: 135 × 0.70 = 94.50, a saving of 40.50.
2. Second discount applies to 94.50, not to 135: 94.50 × 0.90 = 85.05.
3. Total paid: 85.05 versus the sticker 135 — a saving of 49.95.
4. Combined rate: 1 − 85.05/135 = 37%, not the 40% the two numbers suggest.

Order does not matter with two multipliers, but the identity does: discounts compound on whatever base they find, which is why "30% + 10%" is never 40%.

Sale prices on a 120 item

Notice each saving is exactly its discount rate of the original price — the saving column grows linearly even though the paid column does not.

Mistakes discount maths invites

• Adding stacked rates. 30% then 20% is 44% off total, because the second cut bites into the reduced price.
• Computing savings of the sale price. The saved amount is measured against the original; the sale price is the wrong base.
• Trusting the anchor. A lofty "was 299" that nobody paid adds fake savings. Judge the item's real street value instead.
• Comparing 20% off two different prices. Percentages only compare within the same base; two cheaper items can share a rate and different savings.
• Forgetting tax or shipping. A big discount on a small basket can be offset by delivery; the paid figure that matters includes extras.

Keep exploring

• VAT Calculator — add or extract the tax on a price.
• Tip Calculator — the other kind of multiplier people make at the till.
• Percentage Change — measure a price's movement between two dates.
• Guide: How to Calculate Percentages.