In this guide
This guide covers the three discount formulas, three checked examples, the mistakes that trip people up — especially with stacked discounts — and how the Discount and Percentage calculators do the work for you.
- What a discount percentage means
- Discount amount and final price formulas
- Finding the percentage from two prices
- Worked examples, including stacked discounts
- Common mistakes
What a discount percentage means
A discount percentage is the share of the original price that is taken off. A 20% discount means you pay 20 out of every 100 less — so you pay 80% of the original price.
The percentage is always measured against the original price, not the sale price. Keeping that base in mind avoids most discount errors.
Formula 1: the discount amount
Discount amount = Original price × Discount % ÷ 100.
Example (hypothetical prices): a ₹2,000 item at 25% off has a discount of 2,000 × 25 ÷ 100 = ₹500.
Formula 2: the final price
Final price = Original price − Discount amount. Equivalently, Final price = Original price × (1 − Discount % ÷ 100).
Continuing the example: ₹2,000 − ₹500 = ₹1,500, which is the same as 2,000 × 0.75.
Enter the original price and discount percentage to see the amount saved and the final price instantly.Open the Discount CalculatorFormula 3: the discount percentage from two prices
When you know the original and sale prices but not the percentage: Discount % = (Original price − Sale price) ÷ Original price × 100.
Example (hypothetical prices): an item was ₹1,200 and now costs ₹900. The difference is ₹300, and 300 ÷ 1,200 × 100 = 25%. The Percentage Calculator's percentage-decrease mode gives the same answer — enter the original and new price.
Use the percentage decrease mode to find the discount percentage from an original price and a sale price.Open the Percentage CalculatorExample: stacked discounts
Hypothetical example: a ₹5,000 item has 20% off, and then an extra 10% off the reduced price. After the first discount the price is 5,000 × 0.80 = ₹4,000. The second discount takes 10% of ₹4,000, leaving 4,000 × 0.90 = ₹3,600.
The total saving is ₹1,400, which is 1,400 ÷ 5,000 × 100 = 28% — not 30%. Successive discounts multiply rather than add: 0.80 × 0.90 = 0.72, so you pay 72% of the original price.
| Scenario | Original price | Discount | Final price |
|---|---|---|---|
| 25% off | ₹2,000 | ₹500 (25%) | ₹1,500 |
| Price cut to ₹900 | ₹1,200 | ₹300 (25%) | ₹900 |
| 20% + extra 10% off | ₹5,000 | ₹1,400 (28%) | ₹3,600 |
Common discount calculation mistakes
Always ask: percentage of which price?
- Adding stacked discounts together (20% + 10% is 28% off, not 30%).
- Dividing the saving by the sale price instead of the original price.
- Confusing percentage points with percent when comparing two discounts.
- Forgetting whether tax is applied before or after the discount on a bill.
- Rounding the percentage early and carrying the error into the final price.
Conclusion
Discount maths comes down to one base — the original price. Multiply to get the discount, subtract to get the final price, divide the saving by the original price to get the percentage, and multiply stacked discounts rather than adding them.