How this discount calculator works
A discount is a percentage taken off a price. To find the sale price, convert the discount to a decimal and subtract it from one, then multiply by the original price. A 25% discount means you pay 100% − 25% = 75% of the price, so the sale price is the original price × 0.75. The amount you save is simply the original price minus the sale price.
When two discounts are stacked, the second one applies to the already-reduced price rather than the original. That is why "20% off, then an extra 10% off" is not 30% off: the price becomes original × 0.80 × 0.90 = 0.72 of the original, an effective discount of 28%. Sales tax works the other way — it is added after the discount, so the final price is the discounted price × (1 + tax rate).
| Discount | $50 | $80 | $120 | You save on $80 |
|---|---|---|---|---|
| 10% off | $45.00 | $72.00 | $108.00 | $8.00 |
| 20% off | $40.00 | $64.00 | $96.00 | $16.00 |
| 25% off | $37.50 | $60.00 | $90.00 | $20.00 |
| 50% off | $25.00 | $40.00 | $60.00 | $40.00 |
Reference note: figures use standard percentage arithmetic and are rounded to cents for display. Tax rules and rounding can vary by jurisdiction, so treat the after-tax total as an estimate.
Frequently asked questions
- How do I calculate a discount?
- Multiply the original price by the discount as a decimal to get the amount saved, then subtract it from the original price. A 25% discount means you pay 0.75 of the price, so the sale price is the original × 0.75.
- What is 25% off $80?
- 25% off $80 is $80 × 0.75 = $60. You save $20, because 25% of $80 is $20 and $80 − $20 = $60.
- How do I calculate a final price after tax?
- Apply the discount first to get the price before tax, then multiply by one plus the tax rate. A $60 discounted price with 8% tax becomes $60 × 1.08 = $64.80.
- How do stacked / extra discounts work?
- A second discount applies to the already-reduced price, not the original. So 20% off then an extra 10% off is original × 0.80 × 0.90 = 0.72 — a 28% effective discount, not 30%.
- How do I find the original price from a sale price?
- Divide the sale price by one minus the discount as a decimal. A $60 item that was 25% off had an original price of $60 ÷ 0.75 = $80.
- How do I calculate percentage off?
- Subtract the sale price from the original, divide by the original, then multiply by 100. Saving $20 on an $80 item is 20 ÷ 80 × 100 = 25% off.