Percentage Change Calculator
Calculate the conventional percentage change and absolute difference between two signed values.
Guide
What is percentage change?
Percentage change measures the relative difference between a starting value and an ending value. A positive result indicates an increase relative to the starting value, a negative result indicates a decrease, and zero indicates no change.
Formula
Percentage change (%) = ((Ending value − Starting value) ÷ Starting value) × 100. The starting value cannot be zero because division by zero is undefined. This Calculator keeps the sign of the starting value in the denominator.
Worked example
If a value rises from 100 to 125, the absolute difference is 25. Dividing 25 by the starting value of 100 gives 0.25. Multiplying by 100 gives a percentage change of 25%.
Assumptions and limitations
The Calculator uses the conventional signed formula. When the starting value is negative, a result can feel counterintuitive because the negative starting value remains the denominator. It does not replace the starting value with its absolute value or imply a different interpretation for a particular field.
Common questions
Why is zero not allowed as a starting value? Percentage change divides by the starting value, so a zero denominator makes the conventional result undefined. Can I use negative values? Yes. The Calculator accepts signed values and shows a warning when the starting value is negative. Is absolute difference the same as percentage change? No. Absolute difference is the ending value minus the starting value, while percentage change expresses that difference relative to the starting value.
Methodology
The Calculator validates and calculates with exact decimal arithmetic, then rounds only the displayed percentage and difference. It uses the signed starting value exactly as entered, so the result follows the stated formula for positive and negative values.