Percentage Decrease Calculator
The formula
Decrease (%) = (original value − new value) ÷ original value × 100
The decrease is measured relative to the starting value.
Worked examples
- A price drops from €50 to €35: 15 ÷ 50 = 30% off.
- Weight goes from 92 kg to 85 kg: 7 ÷ 92 = 7.6% of body weight lost.
- A household cuts its energy bill from €1,600 to €1,240 a year: 360 ÷ 1,600 = 22.5% saved.
The recovery trap
A fall and the rise needed to recover from it are not the same percentage, because the rise starts from a lower base:
| Fall | Rise needed to recover |
|---|---|
| −10% | +11.1% |
| −20% | +25% |
| −33.3% | +50% |
| −50% | +100% |
| −75% | +300% |
An investment that loses half its value has to double just to get back to where it was — one reason why limiting losses matters so much in finance.
Successive decreases
Two decreases multiply rather than add: −20% followed by −10% gives 0.80 × 0.90 = 0.72, a total decrease of 28%, not 30%. Stacked discounts in shops work exactly the same way.
Related calculations
- New value after a decrease: multiply by (1 − rate). €50 − 30% = 50 × 0.70 = €35.
- Original value before a decrease: divide by (1 − rate). €35 after a 30% cut was 35 ÷ 0.70 = €50.
- Percentage points: an unemployment rate going from 8% to 6% has fallen by 2 points, which is a 25% decrease.
For prices, the discount calculator gives the sale price directly from a percentage.
Frequently Asked Questions
How do I calculate a percentage decrease?
Subtract the new value from the original, divide by the original and multiply by 100. From 50 to 35: 15 ÷ 50 × 100 = 30%.
Why does a 20% drop need a 25% rise to recover?
The rise is calculated on the lower value. From 100 to 80 is −20%, but from 80 back to 100 is +20 on 80, which is +25%.
Can a decrease be more than 100%?
Not for quantities that can't be negative, such as prices: a 100% decrease means the value has reached zero.