Discount

Discount calculator

Find a sale price from a single discount, or the real combined rate when discounts stack — because 50% then 20% is 60% off, not 70%.

at % off =
Final90.00
120 × (1 − 25/100) = 90.00 · save 30.00
Stack discounts (comma or +) =
Off60%
1 − ((1 − 50/100) × (1 − 20/100)) = 60% · naïve sum 70% overstates by 10 pts

Single vs. stacked

Why stacked discounts multiply instead of adding

A single discount is simple: multiply the price by what’s left after the cut. 25% off means you pay 75% — €120 becomes €90. The trap is stacking. When a second discount lands on an already-reduced price, it applies to that smaller number, not the original.

So “50% then 20%” leaves 50% of the price, then 80% of that: 0.5 × 0.8 = 0.40. You pay 40% and save 60% — not the 70% you’d get by adding the two percentages. The gap only widens with more layers.

Single€120 at 25% off120 × 0.75 = €90.00
Stacked · two50% then 20%1 − (0.5 × 0.8) = 60%, not 70%
Stacked · three30% + 20% + 10%1 − (0.7×0.8×0.9) = 49.6%

Where this bites

Coupon-on-sale offers, trade discounts down a supply chain, and “extra % off already-reduced” signage all stack. Reading them as a sum overstates the deal every time. Enter the chain above to see the one rate that actually applies.

Discount questions

How do I calculate a sale price?
Multiply the original price by (1 − discount/100). A €120 item at 25% off is 120 × 0.75 = €90, a €30 saving.
Do stacked discounts add up?
No — they multiply. “50% then 20%” is not 70% off. You take 50% off (leaving 50%), then 20% off that (leaving 80% of it): 0.5 × 0.8 = 0.40, so you pay 40% and save 60%.
Why does the naive sum overstate the saving?
Because the second discount applies to the already-reduced price, not the original. Adding the percentages double-counts. For 50% + 20% the naive sum (70%) overstates the real 60% by 10 points.
Can I stack more than two discounts?
Yes. Enter any chain separated by commas or plus signs (e.g. “30, 20, 10”) and the calculator multiplies the remaining fractions to give the one true combined rate.