Discount Calculator
Find a sale price from an original price and a percent off, recover the original from a sale price, or stack two successive discounts without adding the percents.
Sale price = $64.00
- A 20% discount keeps 80% of the price.
- Sale price = $80.00 × 0.8 = $64.00.
- You save $16.00.
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All calculations run locally in your browser. Your entered values are not sent to an external service.
How to Use the Discount Calculator
Sale from original multiplies the price by (1 − d/100). Original from sale divides the sale price by that factor. Two successive discounts multiplies two factors so you never add the percents.
- Choose the knowns you have.
- Enter dollars and percents from 0 to 100.
- Read the result, the dollars saved, the equivalent single percent off, and the price factor.
A bare “what is 20% of 80” belongs on the Percent Calculator. Converting 0.20 to 20% belongs on the Decimal to Percent Calculator. Adding a percent onto cost belongs on the Markup Calculator. This page is only markdowns — sale price, original, and stacked discounts.
The Markdown Factor
A percent off is the fraction you do not pay. A 20% discount means you pay 80%. That is why the calculator multiplies by 0.80 instead of subtracting 20 from 80 as if they were the same units. Recovering the original divides by the same factor: if $64 is 80% of the ticket price, the ticket was 64 / 0.80 = $80.
Discount Calculator Examples
$80 off 20%
Factor 0.80. Sale = $64. Savings = $16.
$50 off 10%
Sale = $45. Savings = $5.
$64 was 20% off
Original = 64 / 0.80 = $80. The same pair as the first example, run backwards.
20% then 10% on $100
After 20%: $80. After 10% of that: $72. Equivalent single discount: 28%, not 30%.
0% off
The sale price equals the original. The factor is 1.
120% off is rejected
A classroom markdown does not exceed the price. 100% off is $0; more than 100% is out of scope.
Why You Do Not Add Discounts
The second percent applies to the already-reduced price. 20% then 10% is 0.80 × 0.90 = 0.72. Adding 20 + 10 pretends the second 10% is 10% of the original, which it is not. The Percent Calculator’s common-mistakes list flags this; this page computes the stacked result.
Common Discount Mistakes
Adding 20% and 10%
Successive discounts multiply factors. 20% then 10% is 28% off, not 30%.
Subtracting the percent from the dollars
$80 − 20 is $60, but 20% of $80 is $16. Subtract the dollar savings, or multiply by 0.80.
Dividing by the sale factor incorrectly
To undo a 20% off, divide by 0.80, not by 0.20 and not by 1.20.
Treating a tip as a discount
A tip adds a percent. This page only reduces a price. Use the Percent Calculator for 18% of a bill.
A 100% discount when reversing
If the sale price is $0 after 100% off, any original is possible. The calculator will not invent one.
Discount Calculator FAQs
How do you calculate a discount?
Multiply the original price by (1 − d/100). A 20% off $80 is 80 × 0.80 = $64.
How do you find the original price after a sale?
Divide the sale price by (1 − d/100). $64 after 20% off was $80.
Why is 20% then 10% not 30% off?
The second discount applies to the reduced price. The factors multiply: 0.80 × 0.90 = 0.72, which is 28% off.
Is this the same as the Percent Calculator?
No. Percent does “X% of Y,” “A is what % of B,” and percent change. This page is markdowns only.
Does this add sales tax?
No. Tax is a percent on top of a price. Use the Percent Calculator for a tax amount.
Are my numbers sent to a server?
No. The calculation runs locally in your browser.
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Continue with the Markup Calculator, percents, and decimals in the SolverCalc collection.
Reviewed by Prof. Dr. Khalil Mudassar (PhD) · Last updated: [mc_modified_date]
Sources
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Disclaimer
This calculator is intended for general educational and practical use. Review important results before relying on them in professional work.