How to Calculate a Discount Percentage
When you see a "20% off" tag or a sale price that doesn't tell you the original cost, knowing how to calculate the discount percentage yourself puts you in control. This guide explains the math behind it clearly, with practical examples you can try right now.
Want the quick answer? Use the Discount Calculator to get the result instantly.
Quick Answer
To find the discount percentage when you know the original and sale price:
Discount % = ((Original Price − Sale Price) ÷ Original Price) × 100
Example: Original price $100, sale price $75.
((100 − 75) ÷ 100) × 100 = 25%
The item is 25% off.
The Two Key Discount Formulas
There are two scenarios you'll encounter:
1. You know the discount percentage — find the sale price
Formula:
Discount Amount = Original Price × (Discount % ÷ 100)
Final Price = Original Price − Discount Amount
Example: $80 item, 30% off.
Discount Amount = 80 × 0.30 = $24
Final Price = 80 − 24 = $56
2. You know both prices — find the discount percentage
Formula:
Discount % = ((Original − Sale Price) ÷ Original) × 100
Example: Was $120, now $90.
((120 − 90) ÷ 120) × 100 = 25%
Step-by-Step Examples
$50 item at 10% off
- Discount Amount = 50 × 0.10 = $5
- Final Price = 50 − 5 = $45
- You save $5
$200 item at 25% off
- Discount Amount = 200 × 0.25 = $50
- Final Price = 200 − 50 = $150
- You save $50
₹1,000 item at 15% off
- Discount Amount = 1000 × 0.15 = ₹150
- Final Price = 1000 − 150 = ₹850
- You save ₹150
NPR 10,000 item at 25% off
- Discount Amount = 10000 × 0.25 = NPR 2,500
- Final Price = 10000 − 2500 = NPR 7,500
- You save NPR 2,500
Common Mistakes to Avoid
Adding discounts incorrectly. A 20% discount followed by an additional 10% off is not the same as 30% off. Sequential discounts compound:
After 20% off $100 → $80
After 10% off $80 → $72 (not $70)
Confusing discount amount with discount percentage. "Saving $20" and "saving 20%" are different. Always check which the retailer is advertising.
Rounding errors. For prices like $49.99 or discounts like 12.5%, use a calculator for accuracy.
Frequently Asked Questions
How do I find what percentage off something is? Divide the discount amount by the original price and multiply by 100. Example: $15 off a $60 item = (15 ÷ 60) × 100 = 25% off.
What is the formula for a 20% discount? Multiply the original price by 0.20 to get the discount amount, then subtract from the original price. Example: 20% off $85 = $85 × 0.20 = $17 discount → $68 final price.
How do I calculate discount percentage in Excel?
Use the formula =((B1-A1)/B1)*100 where A1 is the sale price and B1 is the original price.
Use the Discount Calculator
Save yourself the math. The Discount Calculator handles both modes — find the sale price from a discount percentage, or find the percentage off from two prices.
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