Discount Calculator
Standing in front of a "25% off" sign, you want two numbers: what you'll pay and what you'll save. Enter the original price and the discount — and if the tag adds an "extra 10% off at checkout", the second field applies it the way the register will: to the already-reduced price.
Sale price after a discount
Example: 25% off 80 is 60 — you save 20.
What a percentage off actually does
A discount keeps the complementary share of the price: sale price = original × (1 − discount ÷ 100). The example above — 60 after 25% off 80 — is computed at build time by the same engine wired to the form, so the copy and calculator can never disagree. For percentage questions beyond shopping (what percent one number is of another, abstract increases), the percentage calculator covers the general cases.
The stacked-discount trap
"20% off, plus an extra 10% off at checkout" is engineered to be misread as 30% off. The register multiplies: the price keeps 0.80 × 0.90 = 0.72 of itself, so 100 falls to 72 — an effective 28% discount. The gap widens with bigger numbers: two 50% discounts leave a quarter of the price, not zero. The calculator reports the effective single percentage so the sign's arithmetic and the receipt's arithmetic can be compared directly.
Beyond the sticker
A discount tells you what the price fell to, not whether it's the better buy — a rival package with a different size can still win after the markdown, which is a unit price comparison. And when the tag only shows the final sale price, the price change calculator can run the discount backwards to recover what the item cost before.
Frequently asked questions
How do I calculate 25% off a price?
Multiply the price by (1 − 25 ÷ 100). An item at 80 becomes 80 × 0.75 = 60, saving 20. The calculator does this for any percentage, including awkward ones like 15% or 33%.
Why is 20% off plus an extra 10% off not 30% off?
Because the second discount applies to the already-reduced price. On 100: 20% off leaves 80, and 10% off that leaves 72 — an effective 28%, not 30%. Retailers know the sign reads bigger than the discount is.
Does the order of stacked discounts matter?
No. Applying 20% then 10% multiplies the price by 0.80 × 0.90, and applying 10% then 20% multiplies by 0.90 × 0.80 — the same product either way. Order only matters when one of the reductions is a fixed amount rather than a percentage.
How do I find the original price from the sale price?
Divide the sale price by (1 − discount ÷ 100) — dividing, not adding the percentage back. A tag showing 51 after 15% off started at 51 ÷ 0.85 = 60. The price change calculator on this site has a dedicated mode for exactly this reversal.
Can a discount be more than 100%?
Not meaningfully — 100% off already makes the item free, and beyond that the store would be paying you. The calculator accepts 0 to 100 and treats a 100% discount as a zero price rather than an error.
Prices you enter are processed on your device only. The discount math is a tested, typed function — the methodology page explains how results are rounded for display.