The math behind the sale tag
Sale price = original × (1 − discount). A 25% discount on $80 leaves you paying $60 and saving $20. Simple enough — but retailers count on shoppers misjudging percentages, especially when discounts stack.
Stacked discounts don't add up
"25% off, then an extra 20% off" is not 45% off. The second discount applies to the already-reduced price: $80 → $60 → $48. That's a $32 saving, or 40% effective — not 45%. Stacked percentages always produce a smaller total discount than their sum, because each one works on a shrinking base. This calculator's "effective total discount" line shows the true figure so a clever-looking sign doesn't fool you.
Smart-shopper checks
- Discount off what? A percentage off an inflated "original" price can beat a smaller discount off a fair one. Compare final prices, not percentages.
- Need vs deal. Saving 40% on something you wouldn't otherwise buy is spending 60%, not saving anything.
- Add tax back. The advertised sale price is usually pre-tax; the register total will be higher.
The only number that matters at checkout is the final amount leaving your account. Percentages are marketing; the total is reality.