Discount calculator
What a percentage off actually costs, what you save, and what stacked discounts really come to — because 20% off then 10% off is not 30% off.
What does it actually cost?
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| You pay | — |
|---|---|
| You save | — |
| Total discount | — |
| After the first discount only | — |
| If the two were simply added | — |
Why "20% off, then 10% off" is not 30% off
It is 28% off. The second discount is taken from the price after the first one, not from the original. On a £60 item: 20% off brings it to £48, then 10% of £48 is £4.80, leaving £43.20. A straight 30% would have been £42. The gap is small on a jumper and considerable on a sofa.
The same arithmetic runs the other way and catches people more often: a price that rises 10% and then falls 10% does not return to where it started. It ends up 1% lower.
Sale price traps worth knowing
"Was" prices. UK guidance expects a "was" price to have been the genuine selling price for a meaningful period. A discount from a price nothing sold at is not a discount.
Per-unit, not per-pack. The larger pack is not always cheaper per item, and the shelf label showing price per 100g is the only reliable comparison. Multibuys frequently work out dearer than the single price on promotion.
Discount codes and VAT. A percentage code is applied to the VAT-inclusive price you see, so the saving you get is the number on the label. Business buyers reclaiming VAT should compare ex-VAT prices instead, where the same code saves proportionally less in real terms.
Common questions
How do I calculate a percentage discount?
Multiply the price by the discount percentage and divide by 100 to get the saving, then subtract it. Or more directly: multiply the price by (100 − discount) ÷ 100 to get what you pay.
Is 20% off then 10% off the same as 30% off?
No. It is 28% off. The second discount applies to the already-reduced price, so stacked discounts always come to less than their sum.
If a price goes up 10% and then down 10%, is it back to the start?
No, it ends 1% below the original. The rise is calculated on the smaller number and the fall on the larger one.
How do I compare two pack sizes?
Divide the price by the quantity to get a price per unit. Larger packs are often but not always cheaper per unit, and promotional multibuys are sometimes dearer than the single item on offer.
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