BEHIND THE NUMBERS
How this calculation works
Sale price = original × (1 − first discount/100) × (1 − second discount/100). Saving = original − sale. Percentage saving = saving ÷ original × 100. Reverse the multiplication to find the original price; a 100% discount has no unique inverse.
Worked example
25% of £100 is £25; the price after the discount is £75.
Example result: £75.00
A negative saving is a price rise
When an alternative costs more than the reference price, the percentage-saving result is negative. The original price remains the denominator.
Stack discounts correctly
A further 10% off an already discounted £80 removes £8, not £10 from the original £100. Two discounts can therefore differ from their simple sum.
Assumptions and rounding
- Both prices refer to equivalent goods and the same included charges.
- Calculations retain full precision until monetary results are displayed.
Questions about this calculator
Why can the reverse calculation reject 100%?
A free final price cannot reveal what the original price was.
Does this remove VAT?
No. Enter comparable VAT-inclusive or VAT-exclusive prices throughout.