How do you calculate a discount percentage?
Multiply the price by the percent off to get the saving, then subtract it. For 25% off $120, the saving is $120 × 0.25 = $30.00 and the sale price is $90.00. Multiplying by 0.75 gets you the sale price in one step.
Sale price = original price × (1 − discount ÷ 100)| Price | 10% off | 20% off | 25% off | 30% off | 40% off | 50% off |
|---|---|---|---|---|---|---|
| $20.00 | $18.00 | $16.00 | $15.00 | $14.00 | $12.00 | $10.00 |
| $50.00 | $45.00 | $40.00 | $37.50 | $35.00 | $30.00 | $25.00 |
| $75.00 | $67.50 | $60.00 | $56.25 | $52.50 | $45.00 | $37.50 |
| $100.00 | $90.00 | $80.00 | $75.00 | $70.00 | $60.00 | $50.00 |
| $150.00 | $135.00 | $120.00 | $112.50 | $105.00 | $90.00 | $75.00 |
| $200.00 | $180.00 | $160.00 | $150.00 | $140.00 | $120.00 | $100.00 |
| $500.00 | $450.00 | $400.00 | $375.00 | $350.00 | $300.00 | $250.00 |
Why 30% off plus 20% off is not 50% off
A second discount applies to the price that is already reduced. On a $200 item, 30% off leaves $140, and another 20% off that leaves $112.00. You saved $88.00, which is 44%, not 50%.
Real discount = 1 − (1 − first) × (1 − second)The order of two percentages makes no difference: 20% then 10% off $100 is $72.00, and 10% then 20% is $72.00. A dollar coupon is different. On a $100 item with 20% off and a $10 coupon, taking the coupon last costs $70.00, and taking it first costs $72.00. The store’s rules decide the order, so the calculator applies coupons last and you may see a small difference at checkout.
What percent off is this sale?
Divide the money saved by the original price. An $80 item on sale at $59.99 is $20.01 off, and $20.01 ÷ $80 is 25%. Choose Both prices in the calculator to do this for any two prices.
You can go the other way too. If an item is $75 after 40% off, the original was $75 ÷ 0.60 = $125.00. Choose The sale price to check it. Adding 40% back to $75 would give the wrong answer of $105.
What percent off is buy one, get one free?
Buy one, get one free is 50% off, but only if you want two. Stores word deals differently, and converting them to a percent off makes them easy to compare.
| Deal | Regular price | You pay | Percent off |
|---|---|---|---|
| Buy one, get one free | $60.00 | $30.00 | 50% |
| Buy one, get one 50% off | $60.00 | $45.00 | 25% |
| Buy two, get one free | $90.00 | $60.00 | 33.3% |
| $50 off $250 | $250.00 | $200.00 | 20% |
The trap in multi-buy deals is that the discount only exists if you buy more. If you only need one item at $30, buy one, get one free doesn't save you anything, and it costs the same $30.
Rewards are worth comparing too. 10% off and then 5% cash back on $100 leaves you $85.50 after the reward, which works like a stacked discount. Cash back usually arrives later, so check the card's terms and whether you'd carry a balance.
Is a big discount really a good deal?
A percent off only tells you how the price compares with the stated original. Three checks tell you more:
- Is the "was" price real? Federal Trade Commission guides warn against advertising a former price that wasn’t actually offered in good faith for a substantial time. A big percentage is less meaningful if the higher price was never really charged. Comparing with other sellers, or checking the item’s price history where you can, is the practical test.
- Compare the final price, not the discount. 40% off at one store can still cost more than 20% off at another.
- Would you have bought it anyway? Money spent on a discounted item you didn’t need isn’t saved. It’s spent. Sometimes the better question is what the full amount could do elsewhere.
Also check the costs that come later. If you put a purchase on a credit card and carry a balance, interest can use up the discount. The credit card interest calculator shows how much.
How do you add sales tax to a discounted price?
Take the discount first, then add tax to the lower price. A $90.00 sale price at 8% has $7.20 of tax, for $97.20 in total. Add your rate under More options, or use the sales tax calculator. States can treat store and manufacturer coupons differently when working out tax, so a receipt may differ slightly.
Common questions
What is 20% off $50?
It's $10.00 off, for a sale price of $40.00.
How do I find the discount between two prices?
Subtract the sale price from the original, then divide by the original. Choose Both prices in the calculator.
Do percentage discounts add together?
Not when they apply one after another. 20% and then 10% is 28% off, not 30%. They only add when a store applies them both to the original price, which the store's terms would state.
Does sales tax apply before or after a discount?
Generally after a store discount, on the lower price. Rules on manufacturer coupons can differ by state.
Can this tell me if a sale is genuine?
No. It can only do the arithmetic on the prices you enter. Compare with other sellers to judge the deal.
Sources
- 16 CFR Part 233, Guides Against Deceptive Pricing · Electronic Code of Federal Regulations
- 16 CFR Part 233, annotated text · Legal Information Institute, Cornell Law School