How to Calculate a Discount
To calculate a discount, multiply the original price by the discount percentage (as a decimal), then subtract that from the original price.
Sale Price = Original × (1 − Discount % ÷ 100)
Worked Example
A jacket originally costs $80 and is on sale for 25% off:
- Discount amount = $80 × 0.25 = $20
- Sale price = $80 − $20 = $60
Stacked Discounts: They Don't Add Up
If a store offers "20% off, plus an extra 10% off at checkout," it's not the same as 30% off. Discounts stack multiplicatively, not additively.
$100 with 20% off = $80. Then 10% off $80 = $72. So the total discount is 28%, not 30%.
To find the combined discount, multiply: 1 − (1 − 0.20) × (1 − 0.10) = 1 − 0.72 = 28%.
Spotting Fake Discounts
Retailers sometimes inflate "original" prices to make discounts look bigger. Here's how to evaluate a real deal:
- Check the historical price using tools like CamelCamelCamel (Amazon) or Honey browser extension.
- Beware "MSRP" pricing — manufacturer's suggested retail price is often higher than the market average.
- Compare to competitors rather than the retailer's own original price.
Frequently Asked Questions
How do I find the percentage off if I only know the original and sale prices?
Use this formula: Discount % = ((Original − Sale) / Original) × 100. For example, if a $100 item is on sale for $75, the discount is ((100 − 75) / 100) × 100 = 25%.
Does this include sales tax?
No — this calculator shows the pre-tax sale price. Your actual checkout total will be slightly higher depending on your local sales tax rate.