MRP, offer price and the discount formula
One formula settles any single offer: discount = MRP × rate, and you pay MRP × (1 − rate). A ₹3,499 jacket at 25% off gives 3,499 × 0.25 = ₹874.75 off, so you pay 3,499 × 0.75 = ₹2,624.25. A ₹2,999 headset at 40% off costs 2,999 × 0.60 = ₹1,799.40. Run line by line across a ten-item festival cart and these two multiplications verify hundreds of rupees in claimed savings before you pay.
The reverse matters equally: original = offer ÷ (1 − rate). A mixer at ₹3,149 after 30% off started at 3,149 ÷ 0.70 = ₹4,498.57 — exposing a claimed was-price of ₹4,999 as inflated. And anchor on planned purchases only: 60% off a ₹8,999 watch you never wanted still costs ₹3,599.60. Discounts create value against a shopping list; everything else is spending disguised as saving.
Stacked offers: why 30% plus 10% is 37%
Site-wide 30% plus an extra 10% on the reduced price multiply rather than add. On a ₹4,999 suitcase the first cut gives 4,999 × 0.70 = ₹3,499.30, the extra 10% removes 3,499.30 × 0.10 = ₹349.93 more, leaving ₹3,149.37. The effective discount is (4,999 − 3,149.37) ÷ 4,999 = 37%, not 40% — the missing 3 points equal ₹149.97 the headline implies but never gives.
The rule is effective rate = 1 − (1 − d1) × (1 − d2): two 20% coupons give 36%, and 50% plus 50% gives 75%, never 100%. Card cashback usually applies on the discounted cart, so ₹500 back on a ₹4,000 cart adds 500 ÷ 4,000 = 12.5% extra, combining to 1 − 0.8 × 0.875 = 30%. And a flat 38% clearance beats a flashy 30% + 10% stack (37%) by about ₹50 on ₹5,000 MRP.
- ₹4,999 at 30% then 10%: ₹3,499.30 → ₹3,149.37, effective 37%
- Stacked formula: 1 − (1 − d1) × (1 − d2), never d1 + d2
- ₹500 cashback on ₹4,000 discounted cart adds 12.5%, not 10%
- Flat 38% beats stacked 30% + 10% on identical MRPs
GST on discounted prices: the correct order
GST applies on the discounted price, not the MRP. A ₹2,499 shoe pair at 20% off sells for 2,499 × 0.80 = ₹1,999.20, and 12% GST is 1,999.20 × 0.12 = ₹239.90, totalling ₹2,239.10. A shopkeeper charging GST on full MRP (2,499 × 0.12 = ₹299.88) before discounting inflates the bill by about ₹60 — always check the taxable-value line.
Inclusive tags need the reverse split: a ₹2,239.10 GST-inclusive bill at 12% means a base of 2,239.10 ÷ 1.12 = ₹1,999.20, with ₹239.90 as tax. The same division unpicks restaurant bills and contractor quotes hiding margin inside all-in figures — while delivery and convenience fees added after discount usually attract GST at the item's slab too.
Unit pricing: the per-gram trick
Big packs are not always cheaper. A 500 g coffee pack at ₹349 costs 349 ÷ 5 = ₹69.80 per 100 g, while 1 kg at ₹649 costs 649 ÷ 10 = ₹64.90 per 100 g — two small packs cost ₹698 versus ₹649, so the large pack genuinely saves ₹49. Without the per-unit step, ₹349 simply looks cheaper.
The reverse trap is common: a 2 kg detergent value pack at ₹459 (₹22.95 per 100 g) loses to a 1 kg pack at ₹219 (₹21.90 per 100 g) by 4.8% per gram despite the value framing. Apply the same division to subscriptions — a ₹299 monthly plan costs ₹3,588 yearly versus a ₹2,999 annual plan saving ₹589 (16.4%), but six months of actual use on monthly billing costs only ₹1,794. Divide by units you will truly consume.
- Coffee: ₹69.80/100g small vs ₹64.90/100g large — large saves ₹49
- Detergent: ₹22.95/100g value pack vs ₹21.90/100g small — small wins
- Annual plans save ~16% only at full utilisation; part-use favours monthly
- Always divide by usable quantity, ignoring gift packs and bonus sachets
Cards, coupons and festival-sale strategy
Rank offers by effective price after all legs, not headline percentage. A ₹24,999 phone at 15% off plus ₹2,000 card discount plus ₹1,500 exchange bonus works out as 24,999 × 0.85 = ₹21,249.15, minus ₹2,000 = ₹19,249.15, minus ₹1,500 = ₹17,749.15 before GST adjustments. A rival flat 25% deal costs ₹18,749.25 — a full ₹1,000 more despite the bigger percentage, because three small stacked legs beat one large one.
Timing adds 5–10%: electronics dip lowest 24–48 hours into festival sales when surprise bank top-ups land, while fashion bottoms on final clearance day. Set a walk-away price before opening any sale page — the lowest tracked price of 90 days minus 5% — and close the tab if the stack cannot beat it. Countdown timers manufacture urgency; a pre-written number restores arithmetic.
Discount mistakes that make you overpay
Mistake one is adding stacked rates: reading 30% + 10% as 40% overpays mentally by ₹150 on ₹5,000 and feels like a win. Mistake two is ignoring the GST base — tax on MRP instead of discounted value donates 2–3% of every bill to the seller. Photograph MRP, discount and taxable value together before paying in sales.
Mistake three is chasing thresholds backwards: adding a ₹499 filler to unlock a ₹300 coupon on a ₹2,700 cart turns ₹2,400 of effective spend into ₹2,899 — paying ₹499 to save ₹300. Mistake four is buying annual or bulk discounts for consumption that never happens, and mistake five is trusting was-prices with no 90-day history: reconstruct with offer ÷ (1 − rate) and wait when the history is missing.
- Never add stacked rates — multiply them: 30% + 10% = 37%
- Verify GST is charged on discounted price, not MRP
- Do not buy fillers costlier than the coupon they unlock
- Reconstruct was-prices with offer ÷ (1 − rate) before trusting them
Discount shopping FAQs
Is a bigger percentage always better? No — percentages need identical bases. A 50% cut on an inflated ₹1,200 MRP costs ₹600, while 30% off the honest ₹799 MRP elsewhere costs ₹559.30. Convert every contender to final payable rupees with GST and fees, then rank the rupees.
Do coupons apply before GST? On compliant invoices seller discounts cut taxable value first and GST follows; post-sale wallet cashbacks do not rewrite the invoice. Hence instant cart discounts beat equal cashbacks by the GST on the difference — ₹500 instant on 18%-slab goods saves an extra ₹90. Once the effective price beats your walk-away number on a planned item, check out; further hunting burns hours for ₹30–50 while stock-outs cost more.
- Compare final payable rupees, never headline percentages alone
- Instant discounts beat cashbacks by the GST on the discount amount
- Set a walk-away price from 90-day history minus 5%
- Buy planned items at the target; ignore everything else on sale