Discount calculator with stacked coupons
Find the sale price, the amount saved and the true discount after stacked coupons and tax — plus reverse modes for the original price or the % off.
- Runs in your browser
- Nothing you enter is sent
- Free, no account
- Discount 1 type
Leave at 0 if the ticket price already includes tax.
Normal for the US and most of Europe. Switch off to tax the full ticket price.
| Step | Price before | Taken off | Price after |
|---|---|---|---|
| 30% off | $89.99 | −$27.00 | $62.99 |
- Original price
- $89.99
- Total discount
- −$27.00
- Discounted price
- $62.99
- You pay
- $62.99
discounted = $89.99 × (1 − 30%) = $62.99 you pay = $62.99
How to use the discount calculator
- Apply discount — enter the ticket price, then one or more discounts. Each discount can be a percentage or a fixed amount, and they stack in the order you list them.
- Find original — you know what you paid and the discount that was applied, and you want the pre-sale price. Useful for expense claims, insurance replacement values and checking a "was" price.
- Find % off — you have the old price and the new price and want the headline percentage.
Every mode shows the working, so you can check the arithmetic rather than trust it.
The discount formulas
saving = price × discount% ÷ 100
sale price = price × (1 − discount% ÷ 100)
original price = paid ÷ (1 − discount% ÷ 100)
discount% = (original − sale) ÷ original × 100
The multiplication form is the one worth memorising. 35% off means you pay 65%, so the shortcut is to multiply by 0.65 rather than to calculate the saving and subtract it.
Stacked discounts never add up
A rail marked "30% off, extra 20% off at the till" is not 50% off. The second coupon applies to the already reduced price:
$100 × 0.70 = $70, then $70 × 0.80 = $56 — an effective 44% off, not 50%.
The general rule for stacking percentage discounts is to multiply the surviving fractions together:
effective fraction = (1 − d₁) × (1 − d₂) × …
| Stacked discounts | Sum of the percentages | Actual discount | $100 becomes |
|---|---|---|---|
| 20% + 10% | 30% | 28% | $72.00 |
| 30% + 20% | 50% | 44% | $56.00 |
| 40% + 25% | 65% | 55% | $45.00 |
| 50% + 20% + 10% | 80% | 64% | $36.00 |
| 70% + 30% | 100% | 79% | $21.00 |
Order does not matter for percentage discounts — multiplication is commutative. It does matter when a fixed-amount coupon is in the mix: "$20 off, then 25% off" is not the same as "25% off, then $20 off". List them in the order the till applies them and the step table will show the difference.
Working backwards is a division, not a subtraction
If you paid $63 after 30% off, the original was 63 ÷ 0.70 = $90. Adding 30% back to $63 gives $81.90, which is wrong, because the 30% was measured against the larger original price. The same asymmetry explains why a 20% discount needs a 25% increase to undo it:
| Discount taken | Increase needed to return to the original |
|---|---|
| 10% | 11.1% |
| 20% | 25.0% |
| 25% | 33.3% |
| 33.3% | 50.0% |
| 50% | 100.0% |
| 75% | 300.0% |
Where sales tax fits
In the United States and in almost every VAT regime, tax is charged on what you actually pay, so a discount reduces the tax too. That is the default here. The switch exists for the rare cases — certain manufacturer rebates and some vehicle purchases in a handful of states — where tax is assessed on the pre-discount price.
Reading a sale sign honestly
- "Up to 70% off" means at least one item is 70% off. Most of the rail will be nearer the bottom of the range.
- "Buy one get one free" is 50% off when you want two items and 0% off when you want one.
- "Buy one get one half price" is 25% off the pair.
- "3 for 2" is 33.3% off, and only if you needed three.
- A "was" price is only meaningful if the item genuinely sold at it. Use the reverse mode to check whether the "was" price is consistent with the percentage claimed.
Privacy
Prices you type stay in this tab. The calculator is plain JavaScript with no network access, so nothing you enter can be collected or profiled.
Questions
Do stacked discounts add together?
No, and that is the single most common shopping mistake. 30% off then a further 20% off is 44% off, not 50%: the second coupon comes off the already-reduced price. The step table shows exactly what each coupon removes.
How do I find the original price from what I paid?
Divide by the surviving fraction rather than adding the percentage back. Paying $70 after 30% off means the original was 70 ÷ 0.70 = $100 — not $91. The "Find original" tab does this, and can strip sales tax out first.
Is sales tax charged before or after the discount?
After, in the US and almost everywhere else — you are taxed on what you actually pay, so a coupon reduces the tax as well. The switch lets you model the rarer case where tax is assessed on the full ticket price.
Why is the percentage back to the original price bigger than the discount?
Because the two percentages are measured against different bases. A 20% discount takes 20% off the original, but recovering it needs 25% added to the smaller sale price. The tool shows both figures side by side.