Percentage Change Calculator
Calculate the percentage increase or decrease between two numbers.
How to use this tool
- Enter original value and new value in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your change and the full breakdown beneath it.
Calculate the percentage increase or decrease between two numbers.
Formula
Percentage Change = ((New Value − Old Value) ÷ Old Value) × 100
A positive result means an increase; a negative result means a decrease.
How it works
This calculator computes the relative change between two numbers by dividing the absolute difference by the original value and expressing the result as a percentage. It applies the standard percentage-change formula used in mathematics, finance, and statistics.
The result is symmetric in direction only — a 50 % increase followed by a 50 % decrease does not return to the starting value, because the base differs. Inputs must share the same unit; the original value must not be zero.
Worked example
- Original value = 100, New value = 150.
- Difference = 150 − 100 = 50.
- Divide by the original value: 50 ÷ 100 = 0.50.
- Multiply by 100 to get a percentage: 0.50 × 100 = 50 %.
Percentage change = 50 % (a 50 % increase).
Common mistakes to avoid
- Using the new value as the denominator instead of the old value — percentage change is always relative to the starting point.
- Confusing percentage change with percentage point change: if a rate goes from 4% to 6%, the percentage change is 50% (not 2%), while the percentage point change is 2.
- Applying the formula when the old value is zero or negative — division by zero is undefined, and negative old values invert the sign of the result.
Key terms
- Original value
- The starting or reference number against which the change is measured.
- Percentage change
- The ratio of the absolute change to the original value, expressed per hundred.
- Absolute change
- The raw arithmetic difference: New Value minus Old Value.
- Relative change
- Another term for percentage change — it scales the absolute change relative to the baseline.
- Negative percentage change
- A result below zero, indicating the new value is smaller than the original (a decrease or loss).
Frequently asked questions
- If a stock goes from $50 to $75, what is the percentage change?
- (75 - 50) / 50 x 100 = +50%.
- What is the percentage change from 100 to 80?
- (80 - 100) / 100 x 100 = -20%, a 20% decrease.
- What if I want to know the new value after a percentage change?
- New Value = Old Value x (1 + Change / 100). For a 15% increase on 200: 200 x 1.15 = 230.