This discount calculator takes an original price and a percent off. Savings equal the price times the percent divided by 100. The sale price equals the original price minus those savings. The headline is the sale price, and the line under it is the amount you save.
The percent comes off the original price once. A second discount taken "20% off the sale price" is not another field, and it is not the same as adding the percents. Two successive 20% discounts remove 36% of the original price, not 40%. Tax and shipping are not added. The sale price here is the merchandise price after the single discount, before the cashier adds anything else.
How to use this calculator
- Enter the original price in US dollars, before the discount.
- Enter the discount as a percent. For 20% off, type 20.
- Press Calculate. Read the sale price in the headline and the savings underneath.
- For a second discount, either run the sale price through the form again or use the stacked-discount steps in the examples.
How a percent-off sale price is calculated
The discount rate is the percent divided by 100. Twenty percent is 0.20. Multiply the original price by that rate to get the savings. Subtract the savings from the original price to get the sale price. Equivalently, the sale price is the original price times (1 − rate). Both descriptions are the same arithmetic, and this form uses the subtract path.
Each of the savings and the sale price is rounded to the cent for display. On many prices they add back to the original. On some prices they miss by a cent, because each line is rounded separately. The worked $79.99 example is one you can check by hand.
A 100% discount saves the entire price and shows a sale price of zero. A discount above 100% produces a negative sale price, which is not a real markdown. A 0% discount saves nothing and returns the original price. The form does not block those entries.
Formula
Savings = original price × discount percent / 100 Sale price = original price − savings Stacked discounts: sale = price × (1 − rate1) × (1 − rate2) Combined percent off = 1 − (1 − rate1) × (1 − rate2), then times 100
Adding percents is the mistake this formula prevents. Twenty percent plus twenty percent is 40 only if both discounts come off the original price. A store that takes 20% off and then 20% off the reduced price multiplies by 0.8 twice. 0.8 × 0.8 = 0.64, so you pay 64% of the original and save 36%.
Display rounding can make the printed savings plus the printed sale price differ from the original by one cent. Trust the formula on the unrounded product if you are checking a till, and expect the on-screen pair to be rounded independently.
Worked discount examples
20% off $100
Savings = 100 × 20 / 100 = 20. Sale price = 100 − 20 = 80. The calculator shows $80.00, and the detail line reads "You save $20.00."
The same sale price is 100 × (1 − 0.20) = 80. Use whichever form is easier to check. There is no tax in that $80. A 8% sales tax, if your store charges it, would be computed by the store on the discounted price or the original price according to local rules. This page does not add it.
15% off $79.99, where cents round
Raw savings = 79.99 × 0.15 = 11.9985, which displays as $12.00. Raw sale price = 79.99 − 11.9985 = 67.9915, which displays as $67.99. The calculator shows $67.99 and "You save $12.00."
In this case $12.00 + $67.99 = $79.99, so the rounded pair adds back. That will not happen for every price. When you compare the screen with a receipt, a one-cent difference in the savings line is consistent with rounding each amount to the cent.
Larger markdowns, and two discounts in a row
Thirty percent off $240 saves 240 × 0.30 = 72, so the sale price is $168.00 and the savings line is $72.00. Fifty percent off $50 saves $25.00 and leaves a sale price of $25.00. Half off means half the original price remains, which is a useful mental check.
Two 20% discounts on $100 are not $40 off. The first sale price is $80. The second discount is 20% of $80, which is $16, so the final price is $64 and the total saved is $36. That is 36% off the original, because 1 − 0.8 × 0.8 = 0.36. To do the second step in this calculator, enter 80 as the original price and 20 as the discount. Entering 40 once would overstate the markdown.
Percent off a $100 original price
| Percent off | You save | Sale price | Fraction of price remaining |
|---|---|---|---|
| 10% | $10.00 | $90.00 | 0.90 |
| 15% | $15.00 | $85.00 | 0.85 |
| 20% | $20.00 | $80.00 | 0.80 |
| 25% | $25.00 | $75.00 | 0.75 |
| 30% | $30.00 | $70.00 | 0.70 |
| 50% | $50.00 | $50.00 | 0.50 |
Tax, coupons, and stacked sales
Sales tax, VAT, shipping, and fees are not in the formula. Some jurisdictions tax the discounted price and some tax the pre-discount price. Add tax only after you know which base applies. Do not type a tax rate into the discount field. That would subtract tax instead of adding it.
A coupon for a fixed number of dollars is not a percent. Subtract that dollar amount yourself. A "20% off, then $10 off" deal is a percent followed by a flat subtraction, which is also not two runs of this form unless you do the percent first and then subtract $10 from the sale price by hand.
Discounts above 100% and negative prices are not blocked. A normal markdown is a percent from 0 through 100. Employee discounts, "buy one get one," and tiered bulk prices often are not a single percent of one original price. Translate them into an effective price before you trust a single rate.
Frequently asked questions
Is the discount taken off the original price?
Yes. One discount percent is multiplied by the original price you enter. Savings on $100 at 20% are $20.00, and the sale price is $80.00. The percent is not applied to a price the form cannot see.
Why is 20% off and then another 20% off not 40% off?
The second 20% applies to the already reduced price. On $100, the first sale is $80 and the second takes $16 more, leaving $64. You save $36, which is 36% of the original, because 0.8 times 0.8 leaves 0.64 of the price. Enter 40 in this form only when a single 40% discount was actually offered.
Does the sale price include sales tax or shipping?
No. The headline is the original price minus the percent savings. Tax and shipping depend on rules this page does not apply. Add them after you have the discounted merchandise price, using the tax base your store actually uses.
What does a 100% discount do?
Savings equal the full original price, and the sale price is $0.00. A $50 item at 100% off shows $0.00 and "You save $50.00." A percent above 100 produces a negative sale price, which is not a normal markdown.
Why might the savings and the sale price look a cent apart from the original?
Each amount is rounded to the cent on its own. Fifteen percent of $79.99 is 11.9985, shown as a $12.00 savings, and the sale price is shown as $67.99. Check a one-cent gap against that rounding before assuming the percent was wrong.