Discount Calculator

The Simple Formula

Working out a discount is straightforward once you know the formula: discount amount = original price × (discount percentage ÷ 100), and final price = original price − discount amount. A worked example: a 30% discount on a £120 item gives a discount of £120 × 0.30 = £36, leaving a final price of £84. You can also find the final price directly by multiplying by (100 − discount)% — so £120 × 0.70 = £84 — which is quicker for a single discount. To work backwards and find the original price from a sale price (useful when only the reduced price and the discount percentage are shown), divide the sale price by (100 − discount)%: a £84 item marked '30% off' was originally £84 ÷ 0.70 = £120. And to find what percentage discount you're getting, divide the saving by the original price and multiply by 100. This calculator handles all these directions. The arithmetic is simple, but the value is in quick, accurate answers when shopping or budgeting — and in checking that a claimed discount matches the actual price reduction, which isn't always the case.

Stacked Discounts

A common and costly misunderstanding is how multiple discounts combine — they don't simply add up. Two separate 20% discounts do not equal 40% off, because the second discount applies to the already-reduced price, not the original. A worked example: 20% off £100 gives £80; then a further 20% off £80 gives £64 — a total saving of £36, which is 36% off the original, not 40%. The more discounts you stack, the more pronounced this effect: three successive 10% discounts give 27.1% off, not 30%. The same logic applies to a discount followed by a tax or surcharge, or a percentage increase after a decrease — they don't cancel out (a 20% rise then a 20% fall leaves you below where you started). To find the combined effect of stacked percentage discounts, multiply the remaining fractions: for two 20% discounts, 0.80 × 0.80 = 0.64, meaning you pay 64% and save 36%. Retailers sometimes advertise 'extra 20% off already reduced prices' precisely because it sounds bigger than it is. This calculator can apply discounts in sequence so you see the true final price, which is often less generous than the headline figures suggest when added naively.

Black Friday & Sales

Research shows many 'original' prices are inflated before sale events. Use price tracking tools to verify whether a sale price is genuinely reduced from a sustained normal price.

Understanding Sale Psychology

Retailers use well-researched pricing psychology that a discount calculator helps you see past. Anchor pricing places a high 'was' price next to the 'now' price to create a perception of value — your brain judges the deal relative to the anchor rather than the item's actual worth, so a high anchor makes any reduction feel generous. This is why UK trading standards require the 'was' price to have been a genuine selling price for at least 28 days beforehand, though the tactic persists. Charm pricing (£9.99 rather than £10) makes prices feel meaningfully lower than they are. Bundle and multi-buy offers like '3 for 2' look like 33% off but only deliver value if you actually need three items — buying extra to 'save' often costs more overall. Time pressure ('sale ends midnight', countdown timers) and scarcity cues ('only 3 left') trigger impulse decisions that bypass careful comparison. Free-shipping thresholds nudge you to add items you didn't intend to buy. The most effective personal defence is simple and behavioural: decide your maximum acceptable price before you see any discount, judge the item on whether you'd pay the final price for it (ignoring the 'saving'), and check the price history. A discount calculator helps by giving you the true final figure and the genuine percentage, so you respond to real numbers rather than the framing.