Discount Calculator — Sale Price & Percent Off Online

Sale price = original × (1 − discount/100); savings = original × discount/100; the two together equal the original. Worked example: 30% off €80 gives sale price = 80 × (1 − 0.30) = 80 × 0.70 = €56 with €24 savings. The percent symbol % is dimensionless per ISO 80000-1:2022 (1 % = 0.01), so the math is unit-agnostic and works the same whether prices are in euros, dollars, yen, or pesos. The page rounds to two decimals (currency precision) and supports decimal discount inputs (e.g., 12.5% off, 33.7% off) for cases where retailers advertise non-round-number reductions.

Discounts compose multiplicatively, not additively: a 20% store discount followed by an extra 10% loyalty coupon equals 0.80 × 0.90 = 0.72, meaning a 28% total reduction from the original price. The naïve "add the percentages" approach (20% + 10% = 30%) overstates the effective discount by 2 percentage points because the 10% coupon applies to the already-discounted price, not the original. Generalisation: stacking N discounts d₁, d₂, ... dₙ yields effective total = 1 − ∏(1 − dᵢ/100). The error compounds with more layers: 20% + 10% + 5% naively = 35% but actually = 1 − 0.80 × 0.90 × 0.95 = 31.6%. The discount-calculator handles arbitrary stacking automatically so users avoid the common pricing error.

United States: FTC 16 CFR Part 233 Guides Against Deceptive Pricing remain codified (rarely enforced by the FTC since the 1970s, but FTC Act § 5 unfair-or-deceptive-practices authority applies regardless), plus 16 CFR Part 238 Bait Advertising (originally 8 November 1967). European Union: Price Indication Directive 98/6/EC Article 6a (introduced by Omnibus Directive 2019/2161, effective 28 May 2022) requires any advertised "reduction" reference the lowest price applied during the preceding 30 days, preventing the inflated-price-then-discount tactic common before the rule. United Kingdom: post-Brexit, the Consumer Protection from Unfair Trading Regulations 2008 (CPRs) and CMA Pricing Practices guidance enforce equivalent reference-price genuineness requirements — "was £X, now £Y" must reflect a real prior selling price recently in force.

Markup and discount use different bases: markup multiplies the cost upward to the selling price, while discount multiplies the selling price downward to the sale price. Pricing a €50 item with a 100% markup: selling price = 50 × (1 + 100/100) = €100. Discounting that €100 selling price by 50%: sale price = 100 × (1 − 50/100) = €50 — back to cost. So a 100% markup is exactly reversed by a 50% discount, NOT a 100% discount. The asymmetry confuses small-business pricing decisions and surfaces in retail tactics like "buy one get one half off" (BOGO 50%) which is a 25% effective discount on the pair, not 50%. The sister markup-calculator (also in this portfolio) computes the inverse direction explicitly.

Prices ending in .99 (or .95, .49) — "charm pricing" or "odd pricing" — exploit a left-digit bias: shoppers anchor on the leading digit and perceive €9.99 as substantively cheaper than €10.00 even though the difference is one cent. Anderson (Chicago GSB) & Simester (MIT Sloan) 2003 retail field experiments published in Quantitative Marketing and Economics 1(1), 93-110, showed about a one-third increase in unit sales when items were repriced from $34 to $39 (no demand difference between $34 and $44 in companion conditions), and the effect held when the .99 ending was bundled with sale signage. Thomas & Morwitz 2005, Journal of Consumer Research 32(1), 54-64, decomposed the left-digit-effect bias into multiple cognitive shortcuts. The discount-calculator does not nudge users toward charm pricing — it shows exact arithmetic — but understanding the anchor lets buyers compare two seemingly different reductions ("25% off €40" vs "€29.99 now") on equal footing.