Percentage Change Calculator
Calculate the signed percentage change from an original value to a new value. The original must be nonzero.
How to use Percentage Change Calculator
1. Enter Original Value, New Value in the stated order. 2. Follow nonzero denominator and whole-number requirements where they apply. Keep corresponding quantities on the same unit scale. 3. Select Calculate or press Enter to see percentage change. 4. Copy result copies the output; Reset clears the inputs and answer.
Why use this tool?
Compare the relative change of two values using the original as the baseline.
How the calculation works
Percentage change = (new value − original value) ÷ original value × 100. Negative baselines follow this algebraic formula and need care when interpreted. Numeric outputs use browser floating-point arithmetic, with two decimal places at most. Smaller nonzero outputs use six significant digits in scientific notation. Unrepresentable intermediate values or numeric outputs beyond the supported magnitude are rejected. Numeric input magnitudes, including each fraction or ratio component, must not exceed 9,007,199,254,740,991. Mathematical references: https://openstax.org/books/prealgebra-2e/pages/4-key-concepts and https://openstax.org/books/prealgebra-2e/pages/6-5-solve-proportions-and-their-applications.
Example
Original Value = 100 and New Value = 120 give 20%. Moving from 120 to 100 gives −16.67%, because the baseline changes.
Practical tip
For scores already expressed as percentages, use a percentage-point difference when that is the intended comparison.
Frequently asked questions
Why can’t I calculate change from zero?
The formula divides by the original value. A zero baseline has no defined relative percentage change, even when the absolute difference is known.
Do signed inputs always have a practical interpretation?
These forms perform the stated arithmetic. Negative values, rates above 100% or a negative baseline can be mathematically valid while being unsuitable for a particular real-world quantity. Check the task and model before applying the result.
Does the tool choose units or round my input first?
Enter corresponding measurements in matching units; the maths forms do not convert units automatically. Exact fraction and ratio text is kept for integer arithmetic. Other numeric operations use browser floating-point values and the display precision stated above.