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Discount Calculator
Sale price, savings, or what % off — all three modes.
Stacked discounts
When two discounts are applied sequentially (e.g. 20% off then an extra 10% off), they don't add to 30%. First discount: $100 → $80. Second 10% off $80: → $72. The effective discount is 28%, not 30%. A combined discount of two sequential percentages is: 1−(1−d1)×(1−d2).
Coupons on already-discounted prices
Same principle — the coupon applies to the already-reduced price, not the original. Stores rely on shoppers mentally adding the percentages and assuming a larger saving than they're getting.
Frequently asked questions
30% off and then 20% off — is that 50% off total?
No. 30% off then 20% off gives a combined discount of 44%, not 50%. Sequential discounts multiply, not add.
How do I find the original price from a sale price?
Use the "Original price?" mode — enter the sale price and discount percentage and it calculates what the original was.
Is a "buy one get one 50% off" better than 25% off everything?
They're equivalent if you buy exactly two items. Buy one get one 50% off is worse if you only want one item, and better if you need four (you save on the 2nd and 4th).
How do I calculate discount without a calculator?
For easy percentages: 10% = move decimal one place left. 20% = double that. 15% = 10% + half of 10%.