Discount Calculator

Enter the sticker price and the percentage off, and the calculator shows two figures: the sale price you actually pay and the amount you keep. It updates as you type and runs entirely in your browser, so it works just as well in a shop aisle as at a checkout page. Read the primary figure as your price before any tax, and the second as the size of the reduction.

How the sale price is worked out

Paying after a discount means keeping the remaining share of the price, so the whole calculation is one multiplication:

sale = price × (1 − d ÷ 100)

The saving is the original price minus the sale price. This is the standard single-discount formula of commercial arithmetic, the same one applied to a trade discount taken off a wholesale list price.

With the defaults — 79.99 at 30% off — the multiplier is 1 − 30 ÷ 100 = 0.70. The sale price is 79.99 × 0.70 = 55.99 (55.993 before rounding to the cent), and the saving is 79.99 − 55.99 = 24.00. The display rounds to the cent; the computation itself keeps full precision. The multiplier is the shortcut worth remembering: subtract the percentage from 100 and read the result as a fraction, and that is the share you still pay. Forty percent off leaves 0.60, fifteen percent off leaves 0.85. To work backwards from a sale price to the original, divide rather than add the percentage back — 55.99 ÷ 0.70 returns 79.99, while adding 30% onto 55.99 gives only 72.79 and understates the original.

Where the percentage comes from

A discount is a percentage, and the percentage is among the oldest tools of commercial arithmetic. Its ancestry runs back to Roman fractions reckoned in hundredths. Augustus levied a centesima rerum venalium, a one-in-a-hundred tax on goods sold at auction, part of the revenue for the military treasury he founded in AD 6, and Roman clerks routinely stated duties and interest as parts of a hundred because doing so made unlike sums comparable. The word itself comes through the Italian per cento, "for each hundred," from the Latin per centum. Medieval and Renaissance merchants worked across a jumble of currencies, weights and local measures, and quoting a rate out of a hundred was the common denominator that let a Florentine and a Flemish trader compare a levy or a markup on equal terms.

The phrase spread through the commercial arithmetic books that accompanied Italian banking, and the written shorthands ran well ahead of any symbol: "per 100," "p 100" and "p cento" already appear in an Italian arithmetic text of 1339. The sign grew out of that shorthand. The historian of mathematics David Eugene Smith, who catalogued these early arithmetics in Rara Arithmetica, traced the first known special mark to an Italian manuscript of 1425, in supplementary pages probably added around 1435, where a scribe compressed per cento into a "p" and "c" carrying a small loop that stood for the Italian ordinal ending in -o. Over the next two centuries the abbreviation drifted: by roughly 1650 the looped "c" had flattened into a horizontal fraction bar with a circle above and below, and the "per" was dropped soon after. The diagonal stroke came later again, and Smith, writing in 1925, said only that the solidus form was modern. The circles in % are therefore the remains of a scribal word ending rather than digits, even if the finished sign reads neatly as a division bar between two zeros.

From trade discounts to the discount store

Reducing a price for a particular class of buyer is as old as wholesaling. A trade discount is the deduction a seller takes off a published list price for a retailer or a bulk buyer, and a cash discount is the smaller reduction offered for prompt payment; both were standard in the ledgers of early modern merchants long before they reached the shop floor. For most of retail history the sticker price was simply the price, held there in many cases by manufacturers who insisted their goods not be sold below a set figure.

Selling to the general public on an openly discounted basis is largely a twentieth-century development. In the postwar United States, Eugene Ferkauf opened a 400-square-foot loft store on East 45th Street in Manhattan in 1948, the start of the E. J. Korvette chain, stocking branded luggage, household appliances and some jewellery at around a third off the usual price. Discounters like it collided with the "fair trade" laws of the day: the federal Miller-Tydings Act of 1937 had sheltered resale-price contracts from the Sherman Act wherever state law allowed them, letting manufacturers enforce a minimum price, and the McGuire Act of 1952 widened that exemption after a Supreme Court ruling had read the first one narrowly. Korvette handed out membership cards outside its stores and to nearby offices so it could style itself a buying co-operative, and the fair-trade suits that established department stores filed against it failed. Those exemptions lost their federal backing when Congress passed the Consumer Goods Pricing Act of 1975, repealing both Miller-Tydings and McGuire, after which the visible percentage-off sale became ordinary retail furniture.

Stacked discounts multiply, not add

An extra 20% off a rack already marked 30% down is not 50% off. The second percentage applies to the already reduced price, so the multipliers combine: 0.70 × 0.80 = 0.56, which is 44% off. To check a stacked offer, either run the calculator twice, feeding the first sale price back in as the new price, or enter the combined figure directly.

The gap widens as the percentages grow, which is why checkout promotions are worded as an extra percentage off.

The was-price is doing psychological work

A crossed-out higher price is an anchor. Once 129.99 is on the tag, 79.99 reads as a 50.00 gain rather than a 79.99 cost, and shoppers judge the deal by the size of the cut instead of asking whether the item is worth the money. Two habits blunt the effect: decide what the item is worth before looking at the discount, and compare final sale prices across shops rather than discount percentages.

Reference-price rules differ by country

Regulators treat the was-price as a factual claim, not decoration.

• EU: Article 6a of the price indication rules, inserted by the Omnibus Directive (EU) 2019/2161 of 27 November 2019 and applied from 28 May 2022, requires any announced reduction to state a prior price, defined as the lowest price the trader charged in a period of at least 30 days before the cut.
• UK: the Omnibus rules never applied in the UK, which had left the EU before they took effect. A was-price is judged under the general ban on misleading actions, now carried by the Digital Markets, Competition and Consumers Act 2024, which replaced the Consumer Protection from Unfair Trading Regulations 2008 in April 2025. There is no fixed 30-day window, but the higher price has to have been a real recent selling price.
• US: the FTC guides against deceptive pricing require a former price to have been openly and actively offered for a reasonably substantial period in the recent, regular course of business. California adds that the former price must have prevailed within the three months before the advertisement, unless the ad states exactly when it did prevail.
• Canada: the ordinary-selling-price provisions of the Competition Act require that a substantial volume was sold at the regular price, or that it was offered in good faith for a substantial time.
• Australia: the ACCC pursues was/now claims where little or nothing actually sold at the higher price.

A percentage off says nothing about whether the reference price was real, so treat advertised discounts as claims to check rather than facts. See the site disclaimer.

Frequently asked questions

How do I calculate 30 percent off 79.99?

Multiply 79.99 by 0.70, because paying after 30% off means keeping 70% of the price. That gives 55.99, and the saving is 24.00. The same shortcut works for any discount: subtract the percentage from 100 and use the result as your multiplier.

Is 30 percent off plus an extra 20 percent off the same as 50 percent off?

No. The extra 20% applies to the already reduced price, so the multipliers combine as 0.70 × 0.80 = 0.56, which is 44% off in total. The gap grows with larger numbers — 50% followed by 30% is 65% off, not 80%.

How do I work back to the original price from the sale price?

Divide the sale price by the fraction you actually paid. If you paid 55.99 after 30% off, the original was 55.99 ÷ 0.70 = 79.99. Adding 30% back onto the sale price is a common mistake — it gives 72.79 and understates the original.

Is sales tax charged on the discounted price or the original price?

In the US and Canada, tax is almost always calculated on what you actually pay after store discounts, so the discount shrinks the tax too. Manufacturer coupons are the awkward exception in some US states, where tax is due on the pre-coupon amount. In the UK, EU and Australia, shelf prices already include VAT or GST, so the percentage off applies to the tax-inclusive price.