Percentage Change Calculator
Percentage Change, Difference and Error Calculator works out Answer for the selected comparison and What the answer is from Comparison type, Initial / accepted / first value and Final / measured / second value. The default figures on this page give answer for the selected comparison of 50 %; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
3 steps
- Change = 75 - 50 = 25
- Divide by the size of the starting value: 25 / 50 = 0.5
- Multiply by 100: 50% (increase)
Its 11 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
2 sources
What the Percentage Change, Difference and Error Calculator calculates
Compares two values and reports the percentage increase or decrease from the first to the second, the symmetric percentage difference between them (which divides by the mean of the two magnitudes, not by the starting value), the percent improvement toward whichever direction is better, and the percent or relative error of a measurement against an accepted value.
How to use this Percentage Change, Difference and Error Calculator
Enter Comparison type, Initial / accepted / first value, Final / measured / second value and Keep the sign of the percent error. Answer for the selected comparison updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Answer for the selected comparison, What the answer is and In words.
The method follows Wikipedia, "Relative change and difference" — relative change uses |x_reference| in the denominator; percentage difference uses the mean of the magnitudes and OpenStax, Chemistry 2e §1.5 "Measurement Uncertainty, Accuracy, and Precision" — percent error = |experimental - accepted| / accepted x 100.
50 rises to 75 example
With Comparison type: change, Initial / accepted / first value: 50, Final / measured / second value: 75, the calculator returns Percentage change: 50, Absolute change (final - initial): 25, Final / initial: 1.5. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Answer for the selected comparison, What the answer is and In words. The inputs you can vary are Comparison type, Initial / accepted / first value, Final / measured / second value and Keep the sign of the percent error.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How to calculate %of change?
Compares two values and reports the percentage increase or decrease from the first to the second, the symmetric percentage difference between them (which divides by the mean of the two magnitudes. Open “How this is worked out” beside the result to see each step for your own figures.
How to do percentage change with a calculator?
It needs Comparison type, Initial / accepted / first value, Final / measured / second value and Keep the sign of the percent error. Nothing else is required, and the figures stay in your browser.
How do I calculate the percentage change between two percentages?
The result gives Answer for the selected comparison, What the answer is, In words, Percentage change, Percentage increase and Percentage decrease, each labelled with its unit so the figure can be read on its own.
What information do I need for the Percentage Change, Difference and Error Calculator?
You need Comparison type, Initial / accepted / first value, Final / measured / second value and Keep the sign of the percent error. The page opens with default figures that give answer for the selected comparison of 50 %, so you can see the scale before entering your own.
What does this Percentage Change, Difference and Error Calculator show?
It shows Answer for the selected comparison, What the answer is, In words, Percentage change, Percentage increase, Percentage decrease, Absolute change (final - initial) and Percentage difference, with the working and any warnings for your entries.
Can I check how the Percentage Change, Difference and Error Calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.