You're standing in a store. Something is 30% off. You want to know the price before you reach the counter. Most people guess. Here's the exact math — three formulas, real examples, and a free calculator that does it instantly.
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Every discount question falls into one of three categories. Here's each one with the formula and a worked example.
This is the most common one. You know the original price and the discount percentage. You want the final price.
The shortcut: subtract the discount percentage from 100, divide by 100, multiply. For 30% off, multiply by 0.70. For 20% off, multiply by 0.80. For 50% off, just halve the price.
This one catches people out. You see a sale price and a discount percentage — and you want to know what it originally cost.
Common mistake: people subtract the percentage from the sale price instead of dividing. That gives the wrong answer. Always divide.
You know what something was and what you paid. You want to know the actual discount percentage.
Don't want to do the math manually? The calculator handles all 3 formulas instantly.
Open Discount CalculatorBookmark this table. It covers the most common discount percentages on prices you'll actually encounter.
| Discount | $25 | $50 | $100 | $200 | $500 |
|---|---|---|---|---|---|
| 5% off | $23.75 | $47.50 | $95 | $190 | $475 |
| 10% off | $22.50 | $45 | $90 | $180 | $450 |
| 15% off | $21.25 | $42.50 | $85 | $170 | $425 |
| 20% off | $20 | $40 | $80 | $160 | $400 |
| 25% off | $18.75 | $37.50 | $75 | $150 | $375 |
| 30% off | $17.50 | $35 | $70 | $140 | $350 |
| 40% off | $15 | $30 | $60 | $120 | $300 |
| 50% off | $12.50 | $25 | $50 | $100 | $250 |
| 60% off | $10 | $20 | $40 | $80 | $200 |
| 70% off | $7.50 | $15 | $30 | $60 | $150 |
This is probably the most misunderstood thing in retail math. Two sequential discounts do not add up to a single combined discount.
Here's why. If an item is 20% off and then an extra 10% off:
The second discount is applied to the already-reduced price, not the original. So 20% + 10% always gives less than 30%.
| Discount 1 | Discount 2 | What People Think | Actual Total |
|---|---|---|---|
| 20% | 10% | 30% | 28% |
| 30% | 20% | 50% | 44% |
| 25% | 25% | 50% | 43.75% |
| 50% | 50% | 100% | 75% |
You don't always have your phone. Here are the fastest ways to estimate discounts in your head:
In the US, sales tax is applied after the discount — not before. So the order matters:
Example: $100 item, 20% off, 8% tax.
If tax were applied before the discount it would be $108 × 0.80 = $86.40 — same in this case, but in some states tax rules differ. Always check your state's tax policy for online purchases.
A 65" TV is listed at $999. The Black Friday price is $699. What percentage off is that?
((999 − 699) ÷ 999) × 100 = (300 ÷ 999) × 100 = 30% off. You save $300.
A jacket is 40% off and costs $54 on the sale rack. What was the original price?
$54 ÷ (1 − 0.40) = $54 ÷ 0.60 = $90 original price.
Cart total is $120. You have a 15% off coupon. How much do you pay?
$120 × (1 − 0.15) = $120 × 0.85 = $102. You save $18.
Two items at $60 each. Second item is 50% off. What's the total?
$60 + ($60 × 0.50) = $60 + $30 = $90 total. Effective discount: 25% off both items.
Need to calculate a specific discount scenario? Use the free calculator — it handles all 3 formulas instantly.
Calculate Your DiscountThis article is for educational purposes. All calculations are based on standard mathematical formulas.