Discount Calculator

How it works

This calculator covers three everyday discount questions, each in its own tab.

Price & percent. Given an original price and a discount percentage, the discount amount and the final price are:

discount amount = original price × discount % / 100
final price = original price − discount amount

Two prices. Given an original price and a discounted (sale) price, the discount percentage is the reverse of the calculation above:

discount % = (original price − discounted price) / original price × 100

The discounted price can't be higher than the original — a "discount" that raises the price isn't a discount, so this is rejected as an input error rather than shown as a negative percentage.

Stacked discounts. This is for two discounts applied one after another, like a storewide 20% off combined with an extra 10% off at checkout. The key point: the second percentage applies to the price that's already been discounted once, not to the original price, so the two percentages don't add up:

price after first discount = original price × (1 − first % / 100)
final price = price after first discount × (1 − second % / 100)
total discount % = (original price − final price) / original price × 100

Because each factor is a fraction less than 1, multiplying them together always gives a smaller final price than either applying the percentages separately or adding them — the combined discount is always a little less than the sum of the two percentages, and equal to it only when one of them is 0%. The order of the two percentages doesn't matter: 20% then 10% and 10% then 20% both land on the exact same final price, since multiplication doesn't care about order.

All amounts are handled as whole cents internally rather than as decimal numbers, and each step is rounded to the nearest cent before the next calculation, so the numbers you see always add up exactly — the final price plus the total discount always equals the original price to the cent.

Examples

Price & percent. An $80 jacket is 25% off. The discount is 80 × 25 / 100 = $20, so the final price is $80 − $20 = $60.

Two prices. A $50 item is on sale for $35. The amount saved is $50 − $35 = $15, which is 15 / 50 × 100 = 30% off.

Stacked discounts. A $100 item first gets 20% off, bringing it to $100 × 0.80 = $80. Then an extra 10% off applies to that $80, not the original $100: $80 × 0.90 = $72. The total discount is $100 − $72 = $28, which is 28% off overall — not 30%, even though 20 + 10 = 30. The second discount is worth less in dollar terms because it's calculated on a smaller price.

Things to watch for

• Stacked discounts multiply, they don't add. "20% off, then an extra 10% off" is 28% off in total, not 30%, because the second percentage is taken from the already-reduced price. This is one of the most common places people overestimate how much they're actually saving.
• The order of two stacked discounts doesn't change the result. Whether the bigger or the smaller discount is applied first, the final price is the same, since multiplying two percentages together is commutative.
• A discounted price can't exceed the original price in the "Two prices" tab — if you're comparing a price increase rather than a discount, this calculator isn't the right tool.
• Amounts are rounded to the nearest cent at each step, half-up, the same way most point-of-sale systems round — this keeps the final price, discount amount, and original price reconciling exactly, but it can occasionally differ from a hand calculation that rounds only once at the end.
• A discount percentage of exactly 100% means free, and 0% means no discount at all — both are valid, not errors.
• Everything runs in your browser. No price you enter is sent to a server; the calculation happens locally on your device.