Percentage Calculator
Find a percentage, percentage change, or reverse percentage.
Your inputs
Your inputs and files stay on your device.
Your result
A little input. A useful answer.
Enter your values and run the tool to see your result here.
How to use it
- Choose the percentage operation you need.
- Enter the two labelled values. Labels change for each operation.
- Calculate and check the result against your input values.
The method
Percent of a value = percentage × value ÷ 100. Percentage change = (new − original) ÷ |original| × 100. Percentage difference uses the average of two non-negative values.
For example
15% of 200 is 30. Increasing 200 by 15% gives 230.
A comparison base of zero is undefined. Reverse percentage divides the final value by 1 + change/100.
Using Percentage Calculator with the right inputs
Find a percentage, percentage change, or reverse percentage. Start by matching your task to the quantities and options shown below. The definitions of the inputs matter as much as the final number or transformed output; retain the original values so that you can repeat or check the result.
Inputs and options explained
- What would you like to calculate?: choose What is X% of Y?, X is what percent of Y?, Percentage change, Percentage difference, Increase a value by a percentage, Decrease a value by a percentage, Find the original value.
- Percentage (X): Enter the percentage in the scale shown by the label; for a field marked %, enter 5 for five percent rather than 0.05.
- Value (Y): Enter the numeric value for this quantity using the units or scale shown in the label.
Example to try in this tool
Use the following sample values to see how the controls and result fit together. They are an illustration of the operation, not recommended values for your own situation.
- What would you like to calculate?: What is X% of Y?
- Percentage (X): 15
- Value (Y): 200
Select Calculate percentage. The result begins with:
Your result
30
First input
15
Second input
This example records the tool’s output for those inputs. Check the method and assumptions against your own task before using a result; reproducing an example is not independent certification of the underlying model.
Interpretation and limitations
Define whether your task concerns calendar dates or elapsed time before comparing results. Inclusive endpoints, local time zones, daylight-saving changes and holiday calendars can lead to different answers. A date calculation does not establish a legal or contractual deadline.
Why can two date tools show different totals?
They may include different endpoints or use different calendars, time zones or working-day definitions. Compare those conventions before treating the difference as an arithmetic error.
Before you use the output
- Choose the intended action: Calculate percentage. Re-run the operation after changing an input or mode so that you are checking the updated result.
- Read the result label and any accompanying explanation. Keep the input values or source file with the output so that a later comparison uses the same assumptions.
- If a result looks unexpected, check units, separators and selected options first. Try a smaller example you can verify rather than repeatedly changing several settings at once.
Questions or a result that needs checking?
If you find a discrepancy, report a problem with Percentage Calculator. Include a non-sensitive example, the selected options, the result you expected and the result shown. This makes the issue easier to reproduce. See About & privacy for how the site handles tool inputs.