Discount Formulas
Sale Price = Original Price × (1 − Discount% / 100)
Savings = Original Price − Sale Price
Discount % = (Savings / Original Price) × 100
Savings = Original Price − Sale Price
Discount % = (Savings / Original Price) × 100
Common Discount Scenarios
| Original Price | Discount | Sale Price | You Save |
|---|---|---|---|
| $100 | 10% | $90.00 | $10.00 |
| $100 | 25% | $75.00 | $25.00 |
| $100 | 50% | $50.00 | $50.00 |
| $250 | 30% | $175.00 | $75.00 |
| $1,200 | 15% | $1,020.00 | $180.00 |
Smart Shopping Tips
- Stack discounts carefully — a 20% discount followed by an additional 10% off is not 30% off. It's 28% off: 100 × 0.8 × 0.9 = 72.
- Calculate cost per unit — bulk discounts are only worth it if you'll use the product before it expires or loses value.
- Compare after-tax prices — a 20% discount on a $100 item at 8% tax = $86.40 final cost. Don't forget tax when comparing deals.
- Watch for anchored pricing — inflated "original" prices make discounts look larger than they are. Research the market price before assuming a discount is genuine.
Frequently Asked Questions
Is 20% off the same as paying 80% of the price?
Yes — a 20% discount means you pay 80% of the original price. This is because Sale Price = Original × (1 − 0.20) = Original × 0.80.
How do I calculate a discount mentally?
For 10% off: move the decimal one place left (10% of $85 = $8.50, so sale price = $76.50). For 25% off: divide by 4 (25% of $80 = $20, so sale = $60). For 50% off: divide by 2.
What is a double discount?
A double discount means two consecutive percentage reductions. Example: 30% off then 10% off = 100 × 0.70 × 0.90 = 63, which is 37% off total — not 40%. Each discount applies to the already-reduced price.
How do I find the original price from a sale price?
Original Price = Sale Price ÷ (1 − Discount Rate). If something costs $60 after a 25% discount, the original was $60 ÷ 0.75 = $80. Use Mode 3 in this calculator for this.