Key takeaways
- check_circleDiscount amount: Multiply the original price by the discount rate: 20% off $80 saves $16.
- check_circleSale price: Pay 100% minus the discount rate: $80 × 0.80 = $64.
- check_circleWith tax: If tax is charged after the discount, apply the discount first: $80 × 1.08 = $86.40.
1. How to calculate a discount
To find the discount amount, multiply the original price by the discount percentage written as a decimal.
Example: 20% off $80
The discount is $80 × 0.20 = $16. The sale price is $80 − $16 = $64. You save $16.
2. Discount calculation table
| Original price | Discount | Savings | Sale price |
|---|---|---|---|
| $50 | 10% | $5 | $45 |
| $100 | 25% | $25 | $75 |
| $250 | 30% | $75 | $175 |
3. How to calculate the final price after a discount
A faster method is to subtract the discount rate from 100%. For 20% off, you pay 80% of the original price: $80 × 0.80 = $64.
4. Discount plus sales tax
If tax is charged after the discount, calculate the sale price first, then apply the tax. For example, a $100 item with 20% off costs $80 before tax. With 8% tax, the final amount is $80 × 1.08 = $86.40.
5. How to find the original price from a sale price
If you know the discounted price and discount rate, divide by the percentage you actually paid. A $72 price after 20% off means you paid 80%, so $72 ÷ 0.80 = $90 original price.
6. Common mistakes
- Applying the percentage to the already-discounted price when the discount is based on the original price.
- Forgetting that tax rules vary and may be applied before or after discounts.
- Rounding too early in a multi-step calculation.
7. Frequently asked questions
How do I calculate a 20% discount?expand_more
Multiply the original price by 0.20 to find the savings, then subtract that amount from the original price.
What is the sale price of $100 after 30% off?expand_more
The savings are $30, so the sale price is $70 before any applicable tax.
How do I calculate price with discount?expand_more
Multiply the original price by 1 − discount rate. For 25% off, multiply by 0.75.