Common Discount Quick Reference
| Original Price | 10% Off | 20% Off | 25% Off | 50% Off |
|---|---|---|---|---|
| $25 | $22.50 | $20.00 | $18.75 | $12.50 |
| $50 | $45.00 | $40.00 | $37.50 | $25.00 |
| $100 | $90.00 | $80.00 | $75.00 | $50.00 |
| $200 | $180.00 | $160.00 | $150.00 | $100.00 |
How to Calculate a Discount
The math is straightforward: multiply the original price by the discount percentage, then subtract that amount from the original. A 25% discount on $80 is $80 × 0.25 = $20 off, leaving a $60 sale price.
When a sales tax applies, it's calculated on the discounted price, not the original. A 10% discount on $100 with 8% tax: sale price = $90, tax = $90 × 0.08 = $7.20, final = $97.20. Applying tax to the pre-discount price would overcharge by $0.80 in this example — a common mistake in manual calculations.
Stacked discounts don't add together. A 20% off plus an additional 10% off isn't 30% off. You apply 20% first ($100 → $80), then 10% of the new price ($80 → $72). The effective discount is 28%, not 30%. This matters when comparing promotions that combine coupon codes with sale prices.