How to calculate a discount — step by step (with a worked example)
A discount is a percentage reduction off the original price, which counts as 100%. You get the final price with the formula price · discount rate ÷ 100 for the saving, then price minus that saving. Worked example: 25% off $80 gives $20 saved and a $60 final price. It is pure Grade 7 percentage arithmetic.
Quick answer
To calculate a discount: discount amount = price · discount rate ÷ 100, and final price = price − discount amount. Example: 25% off $80 is 80 · 25 ÷ 100 = $20 saved, so a $60 final price. If you only know the original and sale price, the discount is (original − sale) ÷ original · 100.
At a glance
| Example | 25% off $80 |
|---|---|
| Method | price · rate ÷ 100, then subtract |
| Steps | 4 |
| Result | $60 ($20 saved) |
| Check | 80 · 0.75 = $60 ✓ |
| Grade level | Grade 7 (ages 12–13) |
Worked example: 25% off $80
We first work out the saving in dollars, then subtract it from the original price.
Four steps to the final price
These four steps work for any discount when you know the original price and the discount rate.
Step 1 · Start
80 − 25%Original price $80, with a 25% discount.Step 2 · · %÷100
80 · 25 ÷ 100Find the discount amount: price times rate divided by 100.Step 3 · − discount
80 − 20Subtract the $20 saving from the original price.Step 4 · Result
= $60Final price $60, saving $20. Check: 80 · 0.75 = $60 ✓
Why the discount formula works
Percent means "per hundred": 25% means 25 ÷ 100 = 0.25. So a quarter of 80 is exactly 80 · 0.25 = 20. You take those $20 off and keep 75% of the price — which is why multiplying by the factor 0.75 lands directly on the final price. The discount always refers to the original price, not the already reduced price.