Percent Error Calculator – Calculate Percentage Error
Compare a measured value with the true value as a percentage.
About the Percent Error Calculator
What is the Percent Error Calculator?
A percent error calculator measures the size of a discrepancy between a measured value and a true or accepted value, as a percentage.
Why use this calculator?
Labs, quality control and experiments all need a standard way to say how wrong a result is. Percent error turns that into one comparable number.
How to use it
- Enter the measured (observed) value.
- Enter the true or accepted value.
- Read the percent error and the signed error.
Formula
Percent error = |measured − true| ÷ |true| × 100.
A negative signed error means the measurement was below the true value.
Frequently Asked Questions
What percent error is acceptable?
It depends on the measurement. Labs often accept 5% in chemistry; physical constants need far tighter agreement.
Should I use relative or absolute?
Percent error is relative by construction. Only use absolute error when comparing measurements across very different scales.
What order of operations does this use?
It follows standard PEMDAS/BODMAS rules: parentheses, exponents, multiplication and division, then addition and subtraction.
How precise are the answers?
The calculator uses double-precision floating-point math (about 15 significant digits) and rounds the display. For exact symbolic results use dedicated algebra software.
Can I enter negative numbers or decimals?
Yes. Negative values, decimals and very large or small numbers are all supported unless a field says otherwise.
What does it mean if I get an error?
Errors usually mean an invalid input, such as division by zero or a negative value where only positives make sense. Check your entries and try again.
What is the difference between population and sample?
A population includes every member of a group; a sample is a subset. Sample statistics use n−1 in the denominator to correct for bias.
When should I use median instead of mean?
Use the median when data contains outliers or is skewed, because it is less affected by extreme values than the mean.
What does standard deviation tell me?
It measures how spread out the values are around the mean. A small standard deviation means the data clusters tightly; a large one means it is more scattered.
Is this calculator free to use?
Yes. Every calculator on this site is completely free, with no hidden fees, no subscriptions and no limits on how many times you can use it.