Complete guide
Reviewed July 2026A discount looks simple - 30% off - until the store stacks a second coupon, adds cashback, or quietly inflates the original price first. Knowing exactly how discounts combine turns you from a shopper who trusts the sign into one who checks the real price.
This calculator gives you the final price and the money saved for any discount, and the guide below covers the situations that trip people up: stacked discounts that multiply instead of adding, reverse-discount math to find an original price, and how to detect a fake 'was' price.
The single most useful idea is the multiplier: a percentage off is the same as multiplying by (1 - rate/100). Master that and every discount problem, however layered, becomes simple arithmetic.
The discount formula
Savings = Original price x discount% / 100 Final price = Original price - Savings Multiplier form: Final = Original x (1 - discount/100)
The multiplier form is the key. A 30% discount means multiply by 0.70; a 15% discount means multiply by 0.85. This makes stacking trivial - you just multiply the multipliers - and reversing easy - you divide instead.
Worked examples
- Simple: Rs 2,000 at 30% off - savings = 2000 x 0.30 = Rs 600; final = Rs 1,400.
- Stacked: 30% then an extra 20% off - final = 2000 x 0.70 x 0.80 = Rs 1,120, a 44% effective discount (NOT 50%).
- Reverse: you paid Rs 1,400 after 30% off - original = 1400 / 0.70 = Rs 2,000.
- With cashback: after the Rs 1,120 stacked price, 5% cashback = Rs 56, net Rs 1,064 - an effective 46.8% off.
Stacked discounts and fake sales
Stacked discounts multiply, they never add. '30% + extra 20%' feels like 50% but is only 44% (0.70 x 0.80 = 0.56). Retailers rely on this misperception. The order doesn't matter for the final price - multiplication commutes - but a coupon applied before tax versus after can change the tax you pay.
| Advertised | Multipliers | Real discount |
|---|---|---|
| 20% + 20% | 0.80 x 0.80 = 0.64 | 36% off |
| 30% + 20% | 0.70 x 0.80 = 0.56 | 44% off |
| 50% + 20% | 0.50 x 0.80 = 0.40 | 60% off |
| 50% + 10% + 5% | 0.50 x 0.90 x 0.95 | 57.25% off |
Using this calculator
- Enter the original price and the discount percentage to get the final price and savings.
- For stacked discounts, apply them one at a time (feed each result back in) or multiply the multipliers.
- To find an original price from a sale price, divide by the multiplier (e.g. sale / 0.70 for 30% off).
- Judge deals on the real market price, not the store's 'was' price.
Common mistakes
- Adding stacked discounts instead of multiplying - 30% + 20% is 44%, not 50%.
- Adding a percentage back to a discounted price to find the original - you must divide, not multiply.
- Trusting an inflated 'was' price as the reference for the saving.
- Ignoring whether a coupon applies before or after tax, which changes the tax due.
- Buying something only because it's discounted - a 60%-off item you don't need still costs money.
Frequently asked questions
Glossary
- Discount
- A reduction from the original price, usually a percentage.
- Multiplier
- (1 - rate/100) - the factor form of a discount, ideal for stacking.
- Stacked discount
- Two or more discounts applied in sequence; they multiply.
- Reverse discount
- Finding the original price from a sale price by dividing by the multiplier.
- Effective discount
- The true total saving as a percentage: 1 - final/original.
- Cashback
- A rebate on the amount paid, stacking on top of discounts.
- Fake sale
- An inflated 'was' price used to exaggerate the discount.
- MRP
- Maximum Retail Price - the ceiling from which discounts are often quoted.
Key takeaways
A discount is multiplication by (1 - rate/100), which makes everything easy: stacked discounts multiply their multipliers (30% + 20% = 44%, not 50%), and reversing to an original price means dividing, not adding back. Judge deals on the genuine market price rather than an inflated 'was' price, count cashback as an extra multiplier, and never buy purely because the percentage looks large.
Enter a price and discount above; then try a second discount on the result and see how far it really is from simply adding the two percentages.