Home / Financial / Discount Calculator
Discount Calculator: Sale Price and Stacked Discounts
Enter the original price and a percentage off to get the sale price and your saving. Add a second discount to see the combined effective discount when two offers stack.
How the sale price is calculated
A percentage discount removes a share of the price. The sale price is original × (1 − discount ÷ 100) and the saving is the original minus the sale price. For 250 less 30%, the sale price is 250 × 0.70 = 175 and you save 75.
Discounts are applied in sequence. The voucher of 15% takes 15% of 175, which is 26.25, leaving 148.75. In total you have saved 101.25 on 250, or 40.5%.
Why stacked discounts do not add up
Two successive discounts of a% and b% combine to 1 − (1 − a)(1 − b), with a and b as decimals. That equals a + b − a × b, so the combined discount is always less than the simple sum unless one of them is zero. The difference is the overlap a × b. With 30% and 15% the sum is 45% but the effective discount is 40.5%.
Order does not change the final price, because multiplication is commutative. Taking 15% first and then 30% gives the same 148.75. What does matter is whether the second offer applies to the reduced price or to the original price. If the shop says both apply to the original, the discounts do add and you would pay 55% of the original.
Checking a deal
- Compare the final prices, not the percentages, when choosing between offers.
- Look at the base. A discount from an inflated "was" price is smaller in real terms than it appears.
- Watch for exclusions. Coupon codes often exclude sale items, delivery, or tax, which this calculator does not know about.
- Tax timing. If sales tax is added at the till, it is usually charged on the discounted price, but rules and store practice differ.
To work out what percentage you saved when you only know two prices, the percentage calculator has a percentage change mode.
Working backwards from a sale price
Sometimes you know the price you paid and the discount and want the original price. Divide the sale price by 1 − discount. For stacked offers, divide by the product of the two remaining fractions. A final price of 148.75 after 30% and 15% off means 148.75 ÷ (0.70 × 0.85) = 250.
The same step helps when a seller shows only a percentage off. If an item is described as 35% off and costs 65, the earlier price was 65 ÷ 0.65 = 100. Checking this against the price you remember is a quick way to spot an inflated reference price.
Worked example
A jacket is priced at 250. It is marked 30% off, and a voucher then takes a further 15% off the reduced price.
Inputs
| Original price | 250 |
|---|---|
| First discount | 30 % |
| Second discount (applied after the first) | 15 % |
Result
You save 101.25, an effective discount of 40.50%.
| Original price | 250.00 |
|---|---|
| Price after the first discount | 175.00 |
| Final price after both discounts | 148.75 |
| Total savings | 101.25 |
| Combined effective discount | 40.50% |
| Simple sum of the two percentages | 45.00% |
- Stacked percentages multiply, they do not add. The second discount applies to the already reduced price.
Financial disclaimer: Results are estimates for planning and education. They are not financial, tax or legal advice. Fees, taxes, rates and rules vary by lender, product and country, so confirm figures with your provider or a qualified adviser before making decisions.
Frequently asked questions
How do I calculate a discount?
Multiply the original price by the discount percentage divided by 100 to get the saving, then subtract it from the original. Or multiply the original by one minus the discount rate.
What is 20% off followed by 10% off?
It is 28% off in total, not 30%, because the second discount applies to the reduced price. A price of 100 becomes 80 and then 72.
Does the order of two discounts matter?
Not for the final price when both are percentages of the current price. 10% then 20% gives the same result as 20% then 10%.
Can I use it for just one discount?
Yes. Leave the second discount at 0 and the result is the ordinary sale price and saving.
How do I find the original price from a sale price?
Divide the sale price by one minus the discount rate. A sale price of 72 after 28% off means an original of 72 ÷ 0.72 = 100.
Related calculators
References and sources
- Basic percentage arithmetic; see any introductory mathematics text on percentage change and successive percentages.