Discount Calculator
Work out a sale price, including stacked discounts and tax.
Prices you enter stay in the page and are never uploaded.
Working out what a sale price actually is turns out to be harder than it looks, and shops are not always in a hurry to make it easier.
More about Discount Calculator
The part almost everybody gets wrong is stacking. A sign saying 20% off, then a further 10% at the till, is not 30% off. The second discount comes off a price that is already smaller, so the real saving is 28%. Two percentages that look like they should add do not, and the gap grows the more discounts are stacked. This tool applies them in order and shows the effective single percentage, which is the number worth knowing.
It also works backwards. Given a sale price and the advertised discount, it tells you what the thing cost before — useful for checking whether a "50% off" price is a real reduction or a restored original. The one case it refuses is 100% off, because at that point the original could have been anything.
Tax is applied after the discount, which is the usual order, and it is clearly an estimate: real receipts depend on the rate for that category in that place, and this tool knows neither.
- Stacked discounts applied in order, with the effective single percentage shown
- Reverse mode: the original price from a sale price and a known discount
- Optional tax, applied after the discount and labelled as an estimate
- Exact zero at a full discount, with no rounding dust
- Money formatted the way the page language writes it
- Impossible inputs refused with a reason, never shown as NaN
How to use it
- 1Enter the original price and the discount.
- 2Add a second discount if the shop is stacking them.
- 3Read the final price and the effective single percentage.
- 4Switch to reverse mode to work back from a sale price instead.
Questions
Is 20% off then 10% off the same as 30% off?
No, it is 28% off. The second discount applies to a price that is already reduced, so the two do not add.
How do I find the original price from a sale price?
Switch to reverse mode and enter the sale price with the advertised discount. It divides rather than multiplying, which is why doing it in your head goes wrong.
Why can I not reverse a 100% discount?
Because a free item gives no information about what it cost. Any original price is consistent with a price of zero.
Is the tax figure accurate?
It is an estimate. Real rates depend on the product category and the jurisdiction, neither of which this tool knows.
In what order are discount and tax applied?
Discount first, then tax on the reduced price. That is the usual order, though some places tax the original.