Sales · 5 min read
How to Calculate a Discount
Percent off the labeled price — then what you actually pay
A percent discount reduces a labeled original price by a fraction of 100. This tutorial walks through amount saved and sale price, using the same $100 at 20% off defaults as the Discount Calculator. Sales tax, coupons stacked on coupons, and “compare at” prices are outside this identity.
Written by the My Calculator Stack editorial team. About our methods
The discount applies to the original price you enter. It does not include sales tax, shipping, or a second coupon unless you fold those into the inputs.
1.What a discount is
A percent-off discount is a fraction of the original price, not a fixed dollar amount unless the ad says otherwise. “20% off $100” saves $20; the sale price is $80. The rate applies to the labeled original you enter. Tax, if any, is usually computed after the discounted amount — this page does not add tax.
2.The formula
Amount saved S is original price P times d/100. Sale price is original minus saved, which is the same as P × (1 − d/100). A 100% discount drives the sale price to zero; a 0% discount leaves the original. Successive percent-off deals multiply, they do not add: 20% then 10% off is not 30% off.
\[ S = P \times \frac{d}{100},\quad P_{\mathrm{sale}} = P - S = P\left(1-\frac{d}{100}\right) \]
3.Worked example
The Discount Calculator defaults to an original price of $100 at 20% off. Saved = 100 × 0.20 = $20. Sale price = 100 − 20 = $80, or 100 × (1 − 0.20) = 80. At 15% off the same $100, saved is $15 and the sale price is $85.
\[ P_{\mathrm{sale}}=100(1-0.20)=80 \]
4.Original vs sale playground
Move the percent-off slider (and the original price if you want). The bars compare original against sale, and the caption substitutes your numbers into saved and sale price. This is a teaching widget — no favorites, no full calculator chrome. Open the Discount Calculator when you want the standalone tool.
Inline playground
You save / sale price
20.00 saved · 80.00 sale
100 × 0.20 = 20; sale = 100 − 20 = 80
Teaching aid only — the percent applies to the labeled original. Tax, shipping, and stacked coupons are not in this identity.
Open the full Discount calculator →5.Open the full calculator
The Discount Calculator uses the same equation, the same $100 / 20% example, and How it works plus FAQ on one page. Add tax afterward if your receipt taxes the discounted amount.
Try it yourself
Open the related calculator and put these formulas to work.