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Formula
Sale price = Original price × (1 − Discount ÷ 100)
- Original price
- the price before any discount
- Discount
- the percentage off, such as 25 for 25% off
- Sale price
- what you pay after the discount, before sales tax
What the discount calculator works out
A discount is a percentage taken off a price. Stores advertise it as “25% off”, “save 40%” or “extra 15% off sale items”, and the number you care about is what you will actually pay. This discount calculator answers the three questions that come up most in shopping:
- Sale price: what does an item cost after a given percent off, and how much do I save? Add an optional second discount to see what a coupon on top of a sale really comes to.
- Percent off: a price went from one amount to another, so what percentage was taken off?
- Original price: I know what I paid and the percent off, so what was the price before the sale?
How to use the discount calculator
- Pick the tab that matches your question.
- For a sale price, enter the original price and the percent off. If there is a second discount, such as a coupon that applies at the register, enter it in the extra discount field.
- For the percent off, enter the original price and the sale price.
- For the original price, enter the price you paid and the percent off.
The result updates as you type, and the working line underneath shows the exact sum so you can check it.
How to calculate a discount by hand
The trick is to multiply by the share you keep rather than working out the savings and subtracting. If something is 35% off, you pay 65% of the price.
For 35% off a $58 item:
- Share you pay = 100% − 35% = 65% = 0.65
- Sale price = 58 × 0.65 = $37.70
- Savings = 58 − 37.70 = $20.30
How to calculate discount percentage from two prices
If a lamp drops from $140 to $105, the saving is $35. Divide the saving by the original price and multiply by 100: 35 ÷ 140 × 100 = 25% off. Always divide by the original price, not the sale price. Dividing by $105 would give 33.3%, which overstates the discount.
Working back to the original price
If you paid $51 after 15% off, you paid 85% of the original. Divide by 0.85: 51 ÷ 0.85 = $60. Adding 15% to $51 gives $58.65, which is wrong, because the 15% was taken from the original price, not from $51.
Sale prices at common discounts
The table gives the price you pay at each discount. Read across from the original price.
| Original price | 10% off | 20% off | 25% off | 30% off | 40% off | 50% off |
|---|---|---|---|---|---|---|
| $20 | $18.00 | $16.00 | $15.00 | $14.00 | $12.00 | $10.00 |
| $50 | $45.00 | $40.00 | $37.50 | $35.00 | $30.00 | $25.00 |
| $75 | $67.50 | $60.00 | $56.25 | $52.50 | $45.00 | $37.50 |
| $120 | $108.00 | $96.00 | $90.00 | $84.00 | $72.00 | $60.00 |
| $300 | $270.00 | $240.00 | $225.00 | $210.00 | $180.00 | $150.00 |
Double discounts: why 20% + 10% is not 30%
When a coupon is applied to an item that is already on sale, the second percentage comes off the reduced price, not the original. That makes the combined discount smaller than the two numbers added together.
| First discount | Extra discount | Combined discount |
|---|---|---|
| 20% | 10% | 28% |
| 25% | 20% | 40% |
| 30% | 30% | 51% |
| 40% | 25% | 55% |
| 50% | 20% | 60% |
The formula is 1 − (1 − first) × (1 − second). For 30% and then 30%, you pay 0.70 × 0.70 = 0.49 of the price, so the total discount is 51%, not 60%. The order of the two discounts doesn’t matter; 10% then 20% gives the same 28%.
Is the discount real?
A percent off is only as good as the “original” price it is measured from. The Federal Trade Commission’s Guides Against Deceptive Pricing say a former-price comparison is fair when the item was really offered at that price for a reasonably substantial period, and misleading when the former price was inflated to make the sale look bigger. When a deal looks unusually large, compare the sale price with what other stores charge rather than with the tag’s “was” price. To compare different pack sizes, the unit price calculator shows which is the better value per ounce or per item.
Real-life uses
- Clearance and coupons: see what a “take an extra 20% off clearance” sign does to an item already marked 40% off (it comes to 52% off in total).
- Comparing two offers: “$15 off $60” and “20% off” sound different, but $15 is 25% of $60, so the dollar coupon is the better deal at that price.
- Checking a receipt: use the percent-off mode to confirm the discount you were promised was applied.
- Budgeting with tax: discounts are taken before sales tax in most states. Add tax to the sale price with the sales tax calculator.
Common mistakes
- Adding stacked discounts together. 25% plus an extra 20% is 40% off, not 45%.
- Dividing by the sale price when finding the percent off.
- Adding the percentage back to find the original price, instead of dividing by what you paid.
- Confusing percent off with percent change. A drop from $80 to $60 is 25% off, but a rise back from $60 to $80 is a 33.3% increase. The percentage change calculator handles increases, and the percentage calculator covers any other percent question.
Worked examples
A jacket at 35% off
A $129.99 jacket marked 35% off.
Inputs (Sale price): Original price = $129.99; Discount = 35 % off
$129.99 × (1 − 35%) = $84.49
Answer: $129.99 with 35% off costs $84.49, a saving of $45.50.
A coupon on top of a sale
A $250 item at 30% off, with an extra 15% coupon applied to the sale price.
Inputs (Sale price): Original price = $250; Discount = 30 % off; Extra discount (optional) = 15 % off
$250.00 × (1 − 30%) = $175.00 $175.00 × (1 − 15%) = $148.75 Combined: 1 − (1 − 30%) × (1 − 15%) = 40.5% off
Answer: $250.00 with 30% off and then an extra 15% off costs $148.75, a saving of $101.25 (40.5% in total).
Working out the percent off
A pair of shoes reduced from $74 to $55.50.
Inputs (Percent off): Original price = $74; Sale price = $55.50
($74.00 − $55.50) ÷ $74.00 × 100 = 25%
Answer: $55.50 instead of $74.00 is 25% off, a saving of $18.50.
Finding the price before a sale
You paid $38.25 after 15% off and want the original ticket price.
Inputs (Original price): Sale price = $38.25; Discount = 15 % off
$38.25 ÷ (1 − 15%) = $38.25 ÷ 0.85 = $45.00
Answer: A price of $38.25 after 15% off means the original price was $45.00.
Free with a 100% discount
Edge case: a promotion that takes 100% off a $19.95 item.
Inputs (Sale price): Original price = $19.95; Discount = 100 % off
$19.95 × (1 − 100%) = $0.00
Answer: $19.95 with 100% off costs $0.00, a saving of $19.95.
Assumptions and limitations
- Prices are shown to the nearest cent. Intermediate steps are not rounded, so a stacked discount gives the same answer as a single combined discount.
- The optional extra discount is applied to the already reduced price, which is how most store coupons on sale items work. The combined discount is 1 − (1 − first) × (1 − second).
- Discounts are percentages from 0% to 100%. Fixed-dollar coupons are not handled; subtract them from the price first.
- In the percent-off mode, the sale price can't be higher than the original price. In the original-price mode, the discount must be below 100%.
- Results are before sales tax. Add tax to the sale price with the sales tax calculator.
Frequently asked questions
How do you calculate a discount price?
Multiply the price by the discount as a decimal to get the savings, then subtract. For 40% off $65, the savings are 65 × 0.40 = $26 and the sale price is $39. In one step, multiply by what you keep, 65 × 0.60 = $39.
How do you calculate discount percentage between two numbers?
Subtract the sale price from the original price, divide by the original price and multiply by 100. A price cut from $85 to $68 is (85 − 68) ÷ 85 × 100 = 20% off.
Is 20% off and then 10% off the same as 30% off?
No. The second discount applies to the reduced price, so you pay 0.80 × 0.90 = 0.72 of the original, which is 28% off in total. Stacked discounts always add up to less than their sum.
How do I find the original price before a discount?
Divide the sale price by the share you paid. If $42 is the price after 30% off, you paid 70%, so the original price was 42 ÷ 0.70 = $60. Use the original-price mode.
Is sales tax calculated before or after a discount?
In most states, sales tax applies to the price you actually pay after a store discount. Manufacturer coupons can be treated differently in some states, so check your receipt or your state's revenue department.
What is the quickest way to work out 25% off in my head?
Take a quarter of the price and subtract it, or multiply by three quarters. 25% off $36 is $36 − $9 = $27.
Sources
- Part 233—Guides Against Deceptive Pricing — Electronic Code of Federal Regulations (Federal Trade Commission, 16 CFR Part 233). Checked October 10, 2026.