Discount Calculator

What's the key thing to understand about 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.

What's the key thing to understand about 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.

What should I know about 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.

What should I know about 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.

How Retailers Use Reference Pricing and 'Was/Now' Tags

A displayed discount is only as meaningful as the reference price it's measured against, and retailers have considerable latitude in how they set that "was" price. Pricing regulations in the UK generally require that a reference price reflect a price the item was genuinely sold at for a reasonable period, rather than an inflated figure invented purely to make a markdown look larger. Even so, a common tactic is to set an unusually high initial price for a short window, then "discount" from that inflated figure to what was always the intended selling price, producing a headline percentage-off figure that looks far more generous than the real saving. Comparison sites and browser extensions that track historical pricing exist partly because of this, letting shoppers check whether an item has genuinely dropped in price or whether the discount is cosmetic. When using a discount calculator to evaluate whether a deal is worthwhile, it's worth separately checking the item's price history where possible, since the percentage saved only tells you the gap between two prices, not whether either of those prices represents good value in absolute terms.

Percentage Off vs Fixed Amount Off: Which Saves You More

Retailers offer both percentage discounts ("20% off") and fixed-amount discounts ("£20 off"), and which one saves more money depends heavily on the price of the item. A fixed discount saves the same cash amount regardless of price, so its relative value shrinks as the item gets more expensive: £20 off a £40 item is a 50% saving, but £20 off a £400 item is only 5%. A percentage discount scales with price, so it saves more in absolute terms the more expensive the item is, making it generally more valuable on big-ticket purchases. This matters when a voucher code offers a choice between the two, or when deciding which of two similar promotions to use: for lower-priced items a flat-amount discount often wins, while for higher-priced items a percentage discount usually comes out ahead. It also explains why many "spend more, save more" fixed-discount vouchers encourage adding extra items to a basket; pushing the subtotal higher doesn't change the fixed saving, so the discount's percentage impact actually falls the more is added, even though the deal is framed as getting better value.

Worked Example: Comparing a Percentage Discount to a Fixed Amount Off

A £180 jacket is offered either at "25% off" or "£40 off" — two offers that sound similar but aren't. 25% off £180 removes £45, bringing the price to £135. £40 off brings the price to £140. The percentage discount saves an extra £5 in this case, because 25% of £180 happens to exceed the flat £40 figure. The crossover point is easy to find: a percentage discount equals a fixed-amount discount exactly when the fixed amount equals that percentage of the price — here, 25% of £160 is exactly £40, so on anything priced above £160, the 25%-off offer saves more, and on anything below £160, the £40-off offer saves more. This is why retailers often apply fixed-amount-off vouchers with a minimum spend threshold set just below this crossover point — it ensures the voucher looks generous on cheaper items (where the fixed amount is a larger relative discount) while limiting how much is given away on the most expensive items in the range, where a percentage-off deal would cost the retailer more.

Converting Discount Percentages to Decimal Multipliers

A quick mental shortcut for discount maths is converting the percentage off into a single decimal multiplier applied directly to the original price, which avoids a separate subtraction step.

For stacked discounts, multiply the multipliers together rather than adding the percentages: 20% off followed by a further 10% off is 0.80 x 0.90 = 0.72, a combined 28% off, not the 30% a quick mental addition might suggest. This gap grows larger the more discounts are stacked, which is worth remembering whenever a retailer advertises several percentage-off codes applied in sequence.