Discount Calculator

Discount formulas

The core calculation is simple. The discount amount is the original price multiplied by the discount percentage expressed as a decimal. The final price is the original price minus the discount amount. These two calculations are all you need to evaluate any single-item percentage discount.

A common error is treating the percentage label alone as the measure of value. A 50% discount on an item priced at 20 saves 10, while a 10% discount on an item priced at 200 saves 20. The percentage matters less than the absolute saving relative to the item’s usefulness and the price available elsewhere.

Comparing discount strategies

Retailers structure promotions in several ways: straight percentage off, fixed amount off, buy-one-get-one, and cashback offers. Straight percentage and fixed-amount offers are directly comparable once you convert both to a final price. A 20% discount on an item priced at 50, which takes 10 off and leaves a final price of 40, is better than a flat 8-off voucher on the same item.

Stacked discounts — applying a percentage reduction to a price that has already been reduced — multiply rather than add. A 20% discount followed by a further 10% off gives (1 - 0.20) × (1 - 0.10) = 0.72, or 28% total off, not 30%. Retailers sometimes present stacked deals in ways that make the combined saving sound larger than it is.

Cashback offers require you to pay full price upfront and receive money back later. The effective discount only materialises if you complete the cashback claim and the payer is reliable. Percentage-off and cashback offers that appear equivalent at face value may differ in convenience, timing, and certainty of the saving.