Discount Calculator
A 20% + 10% sticker doesn't mean 30% off — the second discount applies to the already-reduced price, so the real saving is 28%. This calculator gives you the exact final price and dollar savings for a single discount, and correctly stacks two discounts so you know the true deal before you reach the register.
When to use this calculator
- Finding the final price of a single percent-off sale
- Calculating the real rate when a coupon stacks on top of a sale price
- Comparing a '30% off' deal against a '20% then extra 10%' deal
- Working out how much you actually save before checkout
- Checking a Black Friday or clearance markdown
- Setting a sale price as a retailer to hit a target margin
How it works
1 min readWhat is a discount calculator?
A discount calculator finds the final price after a percentage is taken off, and the amount saved. With a single discount it's a straight percentage; with two stacked discounts the order and base matter, because the second percentage applies to the price that already has the first discount baked in.
How It Works
Enter the original price and one or two discount percentages. Each discount is converted to a multiplier (1 − rate). The price is multiplied by each, so stacked discounts compound rather than add.
Formula
factor = (1 - d1/100) * (1 - d2/100)
finalPrice = originalPrice * factor
savings = originalPrice - finalPrice
realPercent = savings / originalPrice * 100Worked Example
$100 with 20% then an extra 10%:
| Step | Value |
|---|---|
| After 20% off | $100 × 0.80 = $80.00 |
| After extra 10% | $80 × 0.90 = $72.00 |
| Savings | $100 − $72 = $28.00 |
| Real discount | 28% (not 30%) |
Why Stacked Discounts Aren't Additive
Two discounts of d1 and d2 give a combined rate of d1 + d2 − (d1×d2)/100, always less than d1 + d2. For 20% and 10%: 20 + 10 − 2 = 28%. The bigger each discount, the larger the gap from the naive sum.
Limitations
Frequently asked questions
How do I calculate a percentage discount?
Multiply the price by (1 − discount/100). For 20% off $100: $100 × 0.80 = $80. The savings is the difference: $20. This calculator does it instantly and also handles a second stacked discount.
Is 20% + 10% the same as 30% off?
No. The second discount applies to the already-reduced price, so 20% then 10% equals 28% off, not 30%. The combined rate is always less than the sum. The formula is d1 + d2 − (d1×d2)/100.
Does the order of two discounts matter?
For two percentage discounts, no — multiplication is commutative, so 20% then 10% gives the same final price as 10% then 20%. Order only matters when mixing a percentage discount with a fixed-dollar coupon.
How do I find the original price from a sale price?
Divide the sale price by (1 − discount/100). If an item is $72 after 28% off, the original was $72 ÷ 0.72 = $100. To reverse a single 20% discount on an $80 item: $80 ÷ 0.80 = $100.
How much do I save with a discount?
Savings = original price − final price, which also equals original price × discount/100 for a single discount. On a $100 item at 20% off, you save $20.
What is the combined rate of stacking three discounts?
Multiply all the (1 − rate) factors. For 20%, 10%, and 5%: 0.80 × 0.90 × 0.95 = 0.684, so the real discount is 31.6%. This calculator supports two discounts; chain a third by running the output through again.
Should I apply the discount before or after tax?
Discounts are applied to the pre-tax price; sales tax is then calculated on the discounted amount. So a discount also slightly reduces the tax you pay. This calculator shows the pre-tax final price.
How do retailers use discount math to set sale prices?
To hit a target final price from a target margin, retailers solve for the discount: discount = (1 − targetPrice/originalPrice) × 100. Knowing stacked discounts compound helps avoid accidentally giving away more margin than intended.