How to Calculate Discount Percentage - Sale Price Formula

The sign says "50% OFF!" But 50% off what? The MRP? The inflated "original" price? And does the second discount apply to the already-discounted price or the original? Retail math is designed to confuse you into spending more.

Here's how to calculate the actual price you'll pay — and whether that "deal" is actually a deal.

The Discount Formula

Basic Discount

Sale Price = Original Price × (1 − Discount%)

Savings = Original Price − Sale Price

Step-by-Step: ₹2,000 item with 30% discount

1. Discount amount: ₹2,000 × 0.30 = ₹600
2. Sale price: ₹2,000 − ₹600 = ₹1,400
3. You save: ₹600

Quick Mental Math

For 10% off: move the decimal point one place left For 20% off: double the 10% amount For 25% off: divide by 4 For 50% off: divide by 2

Example: ₹1,800 item

• 10% = ₹180
• 25% = ₹450
• 50% = ₹900

Use the Discount Calculator for instant results with any discount percentage.

Double Discounts: The Trap

"Extra 20% off already reduced items!" Sounds like 50% + 20% = 70% off. It's not. The second discount applies to the already-discounted price.

Formula: Sequential Discounts

Final Price = Original × (1 − D1) × (1 − D2)

Example: ₹2,000 item, 30% off + extra 20% off

1. After first discount: ₹2,000 × 0.70 = ₹1,400
2. After second discount: ₹1,400 × 0.80 = ₹1,120
3. Total discount: ₹2,000 − ₹1,120 = ₹880 (44%)

Not 50% — only 44%. The difference is ₹120.

Double Discount Comparison

| Original | 30% + 20% (Sequential) | 50% (Flat) | Difference | |----------|------------------------|-------------|-----------| | ₹1,000 | ₹560 (44% off) | ₹500 (50% off) | ₹60 more | | ₹2,000 | ₹1,120 (44% off) | ₹1,000 (50% off) | ₹120 more | | ₹5,000 | ₹2,800 (44% off) | ₹2,500 (50% off) | ₹300 more | | ₹10,000 | ₹5,600 (44% off) | ₹5,000 (50% off) | ₹600 more |

The Trench Truth: Retailers use sequential discounts precisely because they sound bigger than they are. "30% + Extra 20%" sounds like 50% but saves you less. When comparing deals, always calculate the final price — not the headline discount percentage. A flat 45% off is better than "30% + 20%."

GST on Discounted Items

GST is calculated on the discounted price, not the original. This is a common source of confusion.

Formula

Final Price = Discounted Price + (Discounted Price × GST%)

Example: ₹2,000 item, 30% discount, 18% GST

1. Discounted price: ₹2,000 × 0.70 = ₹1,400
2. GST: ₹1,400 × 0.18 = ₹252
3. Final price: ₹1,652

Wrong calculation: ₹2,000 + ₹360 GST − ₹600 discount = ₹1,760 (overcharges by ₹108)

Flipkart/Amazon Sale Math

During sales, the platform discount and seller discount may be sequential:

Example: ₹3,000 phone with 10% bank offer + ₹300 platform coupon

1. After bank offer: ₹3,000 × 0.90 = ₹2,700
2. After coupon: ₹2,700 − ₹300 = ₹2,400
3. GST (18%): ₹2,400 × 1.18 = ₹2,832

Effective discount: (₹3,540 − ₹2,832) ÷ ₹3,540 = 20% (not the 10% + ₹300 that sounds like 20% of ₹3,000)

Reverse: Finding the Original Price

If you know the sale price and discount percentage:

Original Price = Sale Price ÷ (1 − Discount%)

Example: You paid ₹1,400 after 30% discount

• Original = ₹1,400 ÷ 0.70 = ₹2,000

This is useful for verifying whether a "discounted" price is actually below MRP.

Common Retail Tricks

| Trick | What It Looks Like | Reality | |-------|-------------------|---------| | Inflated original price | "Was ₹5,000, Now ₹2,500" | Original price was never ₹5,000 — it's a manufactured reference price | | Sequential discounts | "30% + Extra 20%" | Only 44% total, not 50% | | BOGO | "Buy 1 Get 1 Free" | 50% off if you need 2 items; 0% off if you need 1 | | Minimum purchase | "20% off on orders above ₹2,000" | You spend more to "save" — net spending increases | | Coupon stacking limits | "Maximum discount ₹500" | On a ₹10,000 item, 10% sounds like ₹1,000 but caps at ₹500 |

Frequently Asked Questions