Original price after 20% off
Enter what you paid and this page works back to the pre-sale price. The discount is fixed at 20% — the price is yours to change.
Worked example at 20% off
You paid £210.00 in a 20% off sale.
- 100% − 20% = 80% of the original price remains
- As a decimal that is 0.8
- 210 ÷ 0.8 = £262.50
- You saved £52.50
Check it forwards: £262.50 − 20% = £210.00 ✓
Adding 20% back to £210.00 would give £252.00 — which is wrong, and wrong by more as the percentage grows. The discount was taken off the larger original, so putting it back on the smaller sale price never reaches it.
Where 20% off shows up
Twenty percent is the most advertised discount in retail. It is the default for a mid-season sale, a Black Friday headline on full-price goods, and most "friends and family" events. It is large enough to drive traffic and small enough to protect margin.
It is also where the classic arithmetic mistake does the most visible damage. A £210 sale price reverses to £262.50, but adding 20% back gives £252 — a £10.50 gap on a single item, and a growing one across a basket.
Looking for 20% VAT rather than 20% off? That is a different calculation — a discount is undone by dividing by 0.8, VAT by dividing by 1.2. Reverse VAT calculator
20% off price table
What twenty common sale prices were before the 20% reduction. Every figure is divided by 0.8.
| You paid | Original price | You saved |
|---|---|---|
| £11.00 | £13.75 | £2.75 |
| £16.00 | £20.00 | £4.00 |
| £21.00 | £26.25 | £5.25 |
| £26.00 | £32.50 | £6.50 |
| £31.00 | £38.75 | £7.75 |
| £36.00 | £45.00 | £9.00 |
| £41.00 | £51.25 | £10.25 |
| £46.00 | £57.50 | £11.50 |
| £51.00 | £63.75 | £12.75 |
| £56.00 | £70.00 | £14.00 |
| £61.00 | £76.25 | £15.25 |
| £66.00 | £82.50 | £16.50 |
| £71.00 | £88.75 | £17.75 |
| £76.00 | £95.00 | £19.00 |
| £81.00 | £101.25 | £20.25 |
| £86.00 | £107.50 | £21.50 |
| £91.00 | £113.75 | £22.75 |
| £96.00 | £120.00 | £24.00 |
| £101.00 | £126.25 | £25.25 |
| £106.00 | £132.50 | £26.50 |
Doing it without a calculator
The shortcut is to add a quarter. You paid 80% of the original, and 1 ÷ 0.8 = 1.25 exactly, so a quarter of what you paid added back gives the original with no rounding at all. On £210 that is 210 + 52.50 = £262.50 — the same answer the long division gives.
The exact method is always the same: divide by 0.8. 20% off leaves 80% of the original, so dividing by 0.8 undoes it precisely. Multiplying, or adding the percentage back on, gives a number that is always too small — and the error grows with the discount.
Frequently asked questions
›Why does adding 20% back not return the original price?
The 20% came off the original, but adding it back applies it to the smaller sale price. On a £210 sale price the correct original is £262.50, not £252.