Enter values and select Calculate.
Calculated result
Calculation steps
Formula and worked example
For a positive original, percentage change = (new − original) ÷ original × 100. For a negative original, this tool divides by |original| so the sign follows numerical direction.
A change from 80 to 100 is +25% and an increase. A change from 100 to 80 is −20% and a decrease because each calculation uses its own original baseline.
Calculations keep full internal precision and use controlled display precision with insignificant trailing zeros removed.
How directional change works
Enter the original reference value first and the new value second.
Positive signed change means the new number is greater; negative signed change means it is lower.
No change produces 0% and is labeled in words as well as numerically.
Use Percentage Difference when neither number should be treated as the original.
Zero and negative original values
Relative percentage change from zero is undefined, so the calculator shows only the absolute change and a clear explanation.
For negative original values, the denominator is the original magnitude: (new − original) ÷ |original| × 100.
That explicit convention makes the sign follow movement on the number line instead of silently reversing direction.
Contexts may use a different convention, so confirm the required definition when negative baselines matter.
Change, increase, and decrease
This page owns general directional comparison.
Percentage Increase focuses on increases and can increase a number by a supplied rate.
Percentage Decrease remains the focused tool for decreases.
These related pages do not replace one another or create synonym routes.
Methodology and limits
This deterministic browser-local tool strictly parses finite numbers and applies the formula stated above. It does not evaluate expressions, execute entered text, call a calculation API, or choose a contextual definition for you.