Discount calculator

The number retailers hope you skip

Focus on "Effective discount", not on the badges on the price tag. Retail promotions are stacked precisely because "30% off plus an extra 20%" sounds like half price to a shopper in a hurry, and it is not. The effective figure tells you what single markdown would have produced the same price, and that is the only fair way to compare a stacked clearance deal against a competitor's flat sale. If store A offers 30% plus 15% extra and store B offers a flat 42%, store B is the better deal, even though A's signage shows bigger numbers.

Here is a mental shortcut you can use in the aisle without pulling up this page: add the two discounts, then subtract their product divided by 100. For 30 and 15, that is 45 minus 4.5, so 40.5% off. It works for any pair, and the correction term is exactly the overlap the retailer is counting on you to ignore.

One more use for the "You save" figure: it is denominated in dollars, which is where discount psychology falls apart. Saving 40% on a $12 phone case is under $5. Saving 8% on a $1,400 laptop is $112. Percentages grab attention; the dollars column is where decisions should happen.

A stacked markdown, worked through

A jacket lists at $249.99, marked 30% off, with a coupon for an extra 15% at checkout. Enter 249.99, 30, and 15. The first discount takes the price to 249.99 x 0.70 = $174.99. The extra 15% then applies to that reduced figure, not the original, giving 174.993 x 0.85 = $148.74. You save $101.25, and the effective discount reads 40.5%, not the 45% the signs imply. On this jacket, the gap between the advertised stack and reality is about $11.

How the math runs

The calculator multiplies the price by (1 - first discount / 100), then multiplies that result by (1 - extra discount / 100). Savings are the original minus the final price, and the effective discount is those savings as a percent of the original, rounded to two decimals. Both discount fields are capped between 0 and 100, and an invalid extra discount is quietly treated as zero rather than breaking the result. When a second discount is present, the line under the price shows each intermediate step so you can see exactly where the money went.

What is out of scope

Sales tax is not included; in the US it is charged on the discounted price, so apply your local rate to the "You pay" figure if you want the register total, or run it through the sales tax calculator. The tool also assumes both discounts are percentage-based. A "$20 off" coupon stacked with a percent discount is a different calculation, and the order it applies in changes the outcome, so check the retailer's terms. Finally, it cannot tell you whether the "original price" was ever real. Anchor pricing, where the sticker was inflated before the sale began, makes any discount math look better than the deal actually is.