The festive season brings banners shouting "Flat 60% off", "Extra 10% today" and "10% instant discount with your card". Knowing how to calculate discount quickly helps you see the real price – and spot when a big number hides a small saving. This guide covers every formula you need, with examples in rupees.
The Basic Discount Formula
Discount amount = Original price × Discount % ÷ 100
Sale price = Original price − Discount amount = Original price × (1 − Discount % ÷ 100)
Example: a pair of shoes costs ₹2,400 with 25% off. Discount = 2,400 × 25 ÷ 100 = ₹600. You pay 2,400 − 600 = ₹1,800. Or in one step: 2,400 × 0.75 = ₹1,800.
The one-step version is handy: for 30% off you pay 70% (multiply by 0.7), for 15% off you pay 85% (multiply by 0.85), and so on.
How to Calculate Discount Percentage
When a shop shows two prices – the MRP struck out and the sale price – use:
Discount % = (Original price − Sale price) ÷ Original price × 100
Example: MRP ₹2,499, sale price ₹1,499. Discount = (2,499 − 1,499) ÷ 2,499 × 100 = 1,000 ÷ 2,499 × 100 = 40.02%. Always divide by the original price, not the sale price – dividing by ₹1,499 would wrongly give 66.7%.
How to Find the Original Price
If you know only what you paid and the discount percentage, work backwards:
Original price = Sale price ÷ (1 − Discount % ÷ 100)
Example: you paid ₹1,800 after 25% off. Original = 1,800 ÷ 0.75 = ₹2,400. A common mistake is to add 25% to ₹1,800, which gives ₹2,250 – wrong, because the 25% was taken from the bigger original number.
Double Discounts: Why 40% + 10% Is Not 50%
"Flat 40% off + extra 10% off" sounds like 50% off. It isn't. The extra 10% applies to the already-reduced price. On a ₹10,000 item: 40% off gives ₹6,000; 10% off ₹6,000 is ₹600; you pay ₹5,400. You saved ₹4,600, which is 46%.
Combined discount = 1 − (1 − d₁) × (1 − d₂)
For 40% and 10%: 1 − 0.6 × 0.9 = 1 − 0.54 = 0.46 = 46%. The bigger the discounts, the bigger the gap between what it looks like and what you get:
This is also called a successive discount, a favourite in competitive exams. A quick shortcut for two discounts a% and b% is: a + b − (a × b ÷ 100). For 40 and 10: 40 + 10 − 4 = 46%.
Stacking Several Offers
During big sales you may combine a sale discount, an extra discount, a coupon and a card offer. Apply them in the order the checkout does – usually percentage discounts first, then flat coupons, then the bank offer on what is left:
Here: 10,000 × 0.6 = 6,000 → × 0.9 = 5,400 → − 200 = 5,200 → bank offer 10% = 520 → ₹4,680. Total saving ₹5,320, or 53.2%.
Bank Offers With a Cap
Card offers almost always have a maximum discount: "10% instant discount up to ₹1,500". The cap means the offer shrinks as the order grows:
Divide the cap by the percentage to find the order value where the cap kicks in: ₹1,500 ÷ 10% = ₹15,000. Above that, the real discount falls. Also check the fine print: many offers need a minimum order value, apply only to credit cards or EMI transactions, are limited to one use per card, or come as cashback weeks later instead of an instant discount.
Buy 1 Get 1 and Other Combo Offers
| Offer | You pay for | You get | Real discount |
|---|---|---|---|
| Buy 1 Get 1 free | 1 | 2 | 50% |
| Buy 2 Get 1 free | 2 | 3 | 33.3% |
| Buy 3 Get 2 free | 3 | 5 | 40% |
| Buy 2 Get 50% off on the 2nd | 1.5 | 2 | 25% |
| Buy 3 for the price of 2 | 2 | 3 | 33.3% |
Formula: Real discount = Free items ÷ Total items × 100. With mixed prices, the free item is usually the cheapest one, so the real discount is lower. Combo offers are good value only if you actually need the extra items.
Common Sale Traps
- Inflated MRP: a "70% off" on a price that was never charged. Check price-history tools or compare with other stores.
- "Up to" discounts: "Up to 80% off" may apply to a handful of items.
- Fees at checkout: delivery, platform, handling and convenience fees can wipe out a small discount.
- No-cost EMI: the interest is usually given back as a discount, but processing fees and GST on interest may still apply. Check with an EMI calculator.
- Exchange offers: a big "exchange bonus" means little if the value for your old device is low.
Do Discounts Reduce GST?
Yes. In India, the price you see includes GST, so when the price drops, the GST inside it drops too. On B2B invoices, GST is charged on the value after any discount shown on the invoice. If a discount is given later as a credit note, GST may be adjusted separately. Use our GST calculator to split any price into the base amount and tax.
Mental Maths Tricks for the Shop Floor
- 10%: move the decimal one place left – 10% of ₹3,450 is ₹345.
- 5%: half of 10%. 20%: double 10%. 15%: 10% + 5%.
- 25%: divide by 4. 33%: divide by 3. 50%: halve it.
- Percentages swap: 8% of 50 = 50% of 8 = 4. Use whichever is easier.
- For anything else, the percentage calculator does it instantly.
Frequently Asked Questions
What is the formula to calculate discount?
Discount = Original price × Discount % ÷ 100, and Sale price = Original price − Discount. For ₹2,400 at 25% off, the discount is ₹600 and you pay ₹1,800.
How do I calculate the discount percentage?
Discount % = (Original price − Sale price) ÷ Original price × 100. For an MRP of ₹2,499 and a sale price of ₹1,499, the discount is 40.02%.
What is 40% + 10% discount?
It is a 46% discount, not 50%. The extra 10% applies to the price after the first 40% off: 1 − 0.6 × 0.9 = 0.46.
How do I find the original price from the discounted price?
Original price = Sale price ÷ (1 − Discount % ÷ 100). If you paid ₹1,800 after 25% off, the original price was ₹2,400.
What is the successive discount formula?
For two discounts a% and b%, the combined discount is a + b − (a × b ÷ 100). For 20% and 10%, it is 20 + 10 − 2 = 28%.
How much is Buy 2 Get 1 free as a discount?
33.3%, because you pay for two items and receive three. Buy 1 Get 1 free is 50%.
Disclaimer: Examples are illustrative. Offer terms – minimum order value, caps, eligible cards and cashback timing – vary by seller and bank, so always read the terms on the checkout page.