Discount Calculator
Calculate the final price after a percentage discount and how much you save. Supports stacking a second discount on top of the first.
How the sale price is calculated
A percentage discount keeps the remaining fraction of the price. With an optional second discount stacked on top:
final = price × (1 − d₁ ÷ 100) × (1 − d₂ ÷ 100)
Your saving is the original price minus the final price, and the effective discount is that saving expressed as a percentage of the original.
Worked example
An item priced at 80 with 20% off: final = 80 × 0.80 = 64,
so you save 16. Add an extra 10% off at checkout and the final becomes
80 × 0.80 × 0.90 = 57.60 — a total saving of 22.40, or 28% of the original.
Stacked discounts don't add up
The second discount is taken from the already reduced price, so percentages multiply rather than add.
20% + 10% = 28% off, not 30%. 30% + 30% = 51%, not 60%. And "50% off plus an extra 50%" is 75% off, never free.
The general shortcut: effective % = d₁ + d₂ − d₁×d₂ ÷ 100. Retail promotions lean on this gap — an
"extra 25% off" banner over a 40% sale sounds like 65% but delivers 55%. Whenever you enter a second
discount above, the calculator flags the true combined figure so you can compare offers honestly.
Quick reference
- 10% off — pay 90%: shift the decimal to find the saving.
- 25% off — pay three quarters of the price.
- Two 20% discounts — 36% off in total, not 40%.
- Reverse check: final ÷ original gives the fraction you paid.
Frequently asked questions
How do I calculate a discount price?
Multiply the original price by (1 − discount ÷ 100). For 20% off an 80 item: 80 × 0.80 = 64, saving 16. Equivalently, the saving is price × discount ÷ 100 and the final price is what's left.
Why isn't 20% + 10% off the same as 30% off?
Because the second discount applies to the already-reduced price, not the original. 20% then 10% means paying 0.80 × 0.90 = 72% of the price — an effective 28% off. A straight 30% off would be cheaper.
How do stores use stacked discounts?
"Extra 10% off sale items" and coupon-on-top-of-sale promotions are stacked discounts. They sound bigger than they are: 50% + 20% is 60% off, not 70%. This calculator shows the true effective percentage whenever you enter a second discount.
How do I find the original price from a sale price?
Divide the sale price by (1 − discount ÷ 100). If something costs 64 after 20% off, the original was 64 ÷ 0.80 = 80.
Can I use this for percent-off plus a fixed coupon?
This tool stacks two percentage discounts. For a fixed-amount coupon (e.g. 5 off), apply the percentage here first, then subtract the coupon from the final price — most retailers apply them in that order too.