Percentage Decrease Calculator
A percentage decrease calculator tells you how much a value has fallen, expressed as a proportion of where it started. Whether a price has dropped, a weight has changed, or a business figure has declined, this tool gives you the answer and shows exactly how it was worked out. Enter the original value and the new, lower value to get started.
The number you are starting from
The lower number after the decrease
Percentage decrease
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Formula
How to use this calculator
Formula
Percentage decrease:
% decrease = ((Original value − New value) ÷ Original value) × 100
Worked examples
Example 1: Energy bill
Original: £180/month → New: £135/month
(180 − 135) ÷ 180 × 100 = 25% decrease (saving £45/month)
Example 2: Weight loss
Original: 196 lbs → New: 176 lbs
(196 − 176) ÷ 196 × 100 = 10.2% decrease
Example 3: Share price
Original: 840p → New: 630p
(840 − 630) ÷ 840 × 100 = 25% fall
How it works
The key point is that you always divide by the original value, not the new one. Dividing by the new value gives a different result and is a common mistake.
There is a fact that surprises most people: recovering from a percentage decrease always requires a larger percentage increase than the decrease itself. Lose 50% and you need a 100% gain to get back. Lose 20% and you need a 25% gain. The reason is that after a decrease, the base you are recovering from is lower, so each percentage point of gain covers less ground.
A concrete example: a share worth £100 falls 50% to £50. To return to £100 you need to gain £50, which is 100% of £50, not 50%. The formula for the recovery percentage needed is: (Decrease% ÷ (100 − Decrease%)) × 100.
| Percentage decrease | Increase needed to recover |
|---|---|
| 10% | 11.1% |
| 20% | 25.0% |
| 25% | 33.3% |
| 30% | 42.9% |
| 50% | 100.0% |
| 75% | 300.0% |
Common uses
- Energy bills: tracking the drop in monthly costs after switching tariff or reducing usage
- Weight loss: measuring progress as a percentage of starting weight
- Investment portfolios: calculating the percentage fall in a fund, share, or pension since its peak
- Business revenue: quantifying a decline in monthly or annual sales compared to a previous period
- Property values: working out how much a property's value has fallen from its purchase price
- Salary changes: calculating the real impact of a pay cut or reduction in hours
- Retail pricing: confirming how much a sale price represents off the original
- Inflation-adjusted figures: finding the real-terms decrease in purchasing power over time
Frequently asked questions
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Subtract the new value from the original value to find the drop. Divide that drop by the original value. Multiply by 100 to convert to a percentage. For example: a price falls from £200 to £150. The drop is £50. Divide £50 by £200 to get 0.25. Multiply by 100 for a 25% decrease.
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The formula is: ((Original value − New value) ÷ Original value) × 100. Divide by the original value, not the new one. Dividing by the new value gives a different result and is a common error.
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A 30% decrease requires a 42.86% increase to recover. After the decrease, the base you are recovering from is smaller, so each percentage point of gain covers less ground. The formula for the recovery percentage is: (Decrease% ÷ (100 − Decrease%)) × 100. For 30%: (30 ÷ 70) × 100 = 42.86%.
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No. A percentage decrease measures how far a value falls as a proportion of the original. The largest possible fall is the entire original value, which gives a 100% decrease and leaves zero. In most real-world contexts a value cannot fall below zero, so a percentage decrease above 100% has no practical meaning.
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Percentage decrease specifically measures a fall and always returns a positive number. Percentage change is the broader concept: a positive result means a rise, a negative result means a fall. Use this calculator when you already know the value has gone down and want a clear, positive figure. Use the Percentage Change Calculator when you want a single tool that handles both directions.
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Last reviewed: May 2026