Reverse percentage calculator
68 after a 15% decrease
80
The original amount was 80: the decrease was 12.
Working
- A 15% decrease means the new amount is 100% − 15% = 85% of the original: a multiplier of 0.85.
- original × 0.85 = 68, so divide: original = 68 ÷ 0.85 = 80.
- Check: 80 × 0.85 = 68.
Your result
80. The original amount was 80: the decrease was 12.
Reverse percentages, step by step
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Your mock plan, in three taps
Reverse percentage: divide by the multiplier. A price of £68 after a 15% reduction was £68 ÷ 0.85 = £80 before it.
Questions people ask
How do you do reverse percentages?
Work out the multiplier and divide by it. After a 30% decrease the amount is 70% of the original, so divide by 0.7.
Why can't I just add the percentage back on?
Because the percentage was of the original amount, not the new one. A £80 item with 15% off costs £68; 15% of £68 is only £10.20, which would give £78.20, not £80.
How do you find the price before VAT?
VAT at 20% means the price including VAT is 120% of the price without it, so divide by 1.2. £150 including VAT is £125 before VAT.
How do you find the percentage change itself?
Divide the change by the original amount and multiply by 100.
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How we work this out
What it does
Find the original amount before a percentage increase or decrease, with the multiplier and the working shown.
An amount after a change and the percentage increase or decrease.
Method
- The multiplier is 1 + the percentage for an increase, or 1 − the percentage for a decrease (as a decimal).
- Original = amount after ÷ multiplier.
- Check by multiplying back.