"30% Off Plus Extra 20% Off" Is Not 50% Off — Retail Math Tricks Explained

2026-07-05

Retailers know most shoppers add percentages. The math multiplies instead — and the difference is their margin.

Trick 1: Stacked discounts

"30% off, plus an extra 20% off at checkout" reads like 50% off. It isn't:

• $100 → 30% off → $70
• $70 → 20% off → $56

Effective discount: 44%. The gap grows with bigger numbers: "50% + extra 30%" is 65% off, not 80%. Our discount calculator has a stacked-discount field that shows the true effective percentage.

Trick 2: The inflated "original" price

A "70% off" deal from a never-charged list price can cost more than a competitor's everyday price. Percentages only mean something relative to a real price — always compare final dollar amounts across stores, not discount percentages.

Trick 3: "Up to X% off"

The word doing the work is up to. Usually one clearance item hits the advertised number while the rest of the sale sits at 10–20%. Treat "up to 70%" as "probably 20%".

Trick 4: Spend thresholds

"$25 off $100" nudges you to add items to reach $100. If your cart was $60, you're not saving $25 — you're spending $15 more than planned (plus whatever the filler item costs beyond its value to you). A discount you had to buy extra things to unlock is a purchase, not a saving.

The two-question defense

Before any "deal":

1. What is the final price in dollars? (Not the percentage.)
2. Would I pay that price if there were no sale sign?

If the answer to 2 is no, the discount didn't save you money — it spent it.