Discount Calculator

The math behind the sale price

Amount saved is the original price times the discount percentage; the final price is what's left after subtracting that. Straightforward, but genuinely handy for comparing sale prices in-store or catching a discount that's smaller than it looks — a $100 item at "20% off" saves $20, not $25, which is an easy number to misjudge in your head under fluorescent lighting.

Stacked discounts don't add up the way they look

"50% off, plus an extra 20% off" is a common store promotion, and it does not mean 70% off. Discounts stack multiplicatively, not additively: 50% off first brings $100 down to $50, then 20% off that $50 brings it to $40 — a 60% total discount, not 70%. Run each discount through separately, applying each one to the result of the last, rather than adding the percentages together.

Working backward from a sale price

Sometimes the number you have is the sale price and the discount percentage, and what you actually want is the original price — useful for spotting whether a "was" price on a tag has been quietly inflated before the markdown. That's a rearrangement of the same formula: original price equals the sale price divided by (1 minus the discount as a decimal). A $60 item marked "25% off" implies an original price of $60 ÷ 0.75 = $80 — if the tag's crossed-out price reads higher than that, the advertised discount is smaller in practice than it's being presented as.

Comparing two different discounts fairly

A bigger percentage off doesn't always mean the better deal once prices differ — 30% off a $40 item ($12 saved, $28 final) can lose to 20% off a $70 item that's actually the better per-unit buy, depending on quantity or size. When comparing two similar products at different discounted prices, the final price and, where relevant, the price per unit (per ounce, per item, per use) is the number that actually decides which is the better deal — not the headline percentage either one advertises.