Discount Calculator
The price after a discount, what you save, and what a second discount on top actually comes to.
Runs entirely in your browser. Nothing is uploaded, logged or stored.
100.00
80.00
You save 20.00
-20.00 %
- Original price 100.00
- After the first discount
- Price to pay 80.00
One discount is straightforward. Two stacked discounts are where shops and shoppers disagree, so the effective total is shown alongside the price.
How it works
The first discount comes off the original price. A second discount, where one applies, comes off the already reduced price, which is how "an extra 20% off sale prices" works at the till.
That is why the two do not add up. 20% off and then a further 20% off is not 40% off: it leaves 80% of 80%, which is 64% of the original — an effective discount of 36%.
Examples
| Case | Input | Result |
|---|---|---|
| A single reduction | 100 less 20% | 80 |
| Two stacked reductions | 100 less 20% then 20% | 64, a 36% discount |
Frequently asked questions
Why is 20% off twice not 40% off?
Because the second discount is taken on a smaller price. Each one keeps 80% of what came before, and 80% of 80% is 64%. Stacked discounts always come to less than their sum.
What about tax?
Not included. Whether tax is shown in the price and whether a discount applies before or after it depends on the country, so the tool works on the figure you give it.
Good to know
- Amounts carry no currency: the answer is in whatever you put in.
- Results use double precision floating point arithmetic. That is exact enough to decide with and is not an accounting record.