How to Calculate a Discount and the Sale Price

A discount is a percent of the original price that comes off. You can find the amount saved, then subtract it, or go straight to the sale price by paying the rest.

Try it with your own problem ↓

The steps

Change the discount percent to a decimal: 20% = 0.20.
Multiply it by the original price to get the amount saved.
Subtract the amount saved from the original price to get the sale price.
Shortcut: if the discount is 20%, you pay 100% − 20% = 80%, so multiply the price by 0.80.

A worked example

A $45 jacket is 20% off. What do you pay?

Change 20% to a decimal: 0.20.
Amount saved: 0.20 × 45 = 9, so you save $9.00.
Sale price: 45 − 9 = 36.
Check with the shortcut: you pay 80%, and 0.80 × 45 = 36.

You save $9.00 and pay $36.00.

Why it works

A price is 100% of itself. Taking 20% off leaves 80%, so the sale price is 0.80 times the original. Both methods give the same number, so use whichever is easier to do in your head.

Try it with your own problem

Open the free The Hundred Grid with this example already filled in. It shows every step, and you can type over it with your own numbers.

Work it out: 20% off 45Opens The Hundred Grid with this example

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Common mistakes

Giving the discount as the price. The amount saved ($9) is not what you pay ($36).
Adding two discounts. 20% off and then another 15% off is not 35% off. The second percent is taken from the already-lowered price.
Taking the percent from the sale price. The percent always applies to the original price.
Forgetting tax. Sales tax is added after the discount, to the sale price.

Questions people ask

How do I take 20% off quickly?

Find 10% by moving the decimal point one place (4.50), double it (9.00), and subtract from the price.

What if there are two discounts in a row?

Apply them one at a time. 20% off then 15% off $80 is 80 × 0.80 × 0.85 = $54.40.

How do I find the original price from the sale price?

Divide the sale price by what you paid as a decimal: $36 ÷ 0.80 = $45.

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