Discount Calculator

A discount calculator answers what you actually pay, and the second, more useful question of what the advertised percentage really amounts to once more than one discount is involved. Stacked discounts are the common trap: 25% off followed by an extra 10% off is not 35% off. The second reduction applies to the already-reduced price, so the true combined discount is 32.5%. Retailers rely on the intuition being wrong. This calculator handles a single discount or two stacked ones, showing the final price, the amount saved and the effective total discount as a percentage of the original. That last figure is the one to compare offers on, because it is the only number that makes 'extra 10% off sale items' comparable with a flat reduction.

How this is calculated

A single discount: sale price = original × (1 − discount). Two stacked discounts: sale price = original × (1 − first) × (1 − second). The effective total discount is 1 − (1 − first) × (1 − second).

Worked example on a $200 item at 25% off then a further 10% off: 200 × 0.75 = $150, then 150 × 0.90 = $135. You saved $65, which is 32.5% of the original — not the 35% the two percentages suggest.

The order does not matter. Applying 10% first and 25% second gives the same $135, because multiplication commutes. This is worth knowing when a cashier applies coupons in an order you did not expect.

Why stacked discounts are always worth less than they sound

The shortfall grows with the size of the discounts. 10% plus 10% gives 19%, not 20% — a small gap. 50% plus 50% gives 75%, not 100%, which is the extreme case that makes the principle obvious.

The general rule: stacked discounts always total less than their sum, and the gap is the product of the two rates. For 25% and 10%, that is 0.25 × 0.10 = 2.5 percentage points, exactly the difference between the intuitive 35% and the real 32.5%.

Comparing offers that are not in the same form

Convert everything to an effective percentage off the original price. A '$50 off $200' offer is 25%. 'Buy one get one half price' on two identical items is 25% off the pair. 'Buy two get one free' is 33.3% off three.

Once every offer is expressed that way, they are directly comparable, and the largest headline number frequently is not the best deal. This matters most where a percentage discount is offered against a price that was recently raised — the effective saving against the genuine market price may be nothing at all.

How to use the discount calculator

Enter the original price. The pre-discount price, before any reductions are applied.
Enter the first discount. As a percentage. For a fixed-amount offer, divide the amount by the original price to get the equivalent percentage.
Add a second discount if one applies. The calculator stacks it multiplicatively and reports the effective combined discount, which is the number to compare offers on.

Frequently asked questions

Do two discounts add together?

No — they stack multiplicatively. 25% off then 10% off is 32.5% total, not 35%: the second discount applies to the already-reduced price.

Does the order of two discounts matter?

No. Multiplication commutes, so 25% then 10% gives exactly the same final price as 10% then 25%. If a cashier applies coupons in an unexpected order, the total is unaffected.

How do I convert a fixed-amount discount to a percentage?

Divide the amount saved by the original price. $50 off a $200 item is 50 ÷ 200 = 25%. Doing this makes fixed-amount and percentage offers directly comparable.

What is 'buy one get one free' as a percentage?

50% off two items. 'Buy one get one half price' is 25% off the pair, and 'buy two get one free' is 33.3% off three. Converting multi-buy offers to an effective percentage is the only reliable way to compare them against a straight discount.