Practical tools for measured work
Percentage calculator
Calculate percent of a value, reverse percentages, change, difference and percentage tables.
Calculate the layout, check the diagram, then print the result for the shop or jobsite.
How it works
Percent of a value is p × whole / 100. To recover the whole, divide the part by p/100. Percentage change is (new − original) / original × 100. Percentage difference is absolute difference divided by the mean of two nonnegative values.
Current-input example
The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.
- Percentage operation
- Percent of a value
- Percentage
- 20
- Whole value
- 50
Primary result: Result: 10.
Before using the result
- Check the selected mode, units and input values before using the result.
- Read the assumptions and rounding rules; compare the worked example with your intended calculation.
- A numerical result does not supply missing context or change the stated limitations.
Limitations
Percentage change requires a positive original value. Percentage difference requires nonnegative values with a positive sum. Recovering a whole or a percentage cannot divide by zero. The table lists 5% through 100% in steps of 5%.
Frequently asked questions
Are the displayed decimals exact?
Fractions, combinations and integer multiples use exact integer arithmetic. Other results use floating-point arithmetic and are rounded for display. Keep the exact fraction when a repeating decimal matters.
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