How do you calculate percent error?

Divide the absolute difference between measured and accepted values by the magnitude of the accepted value, then multiply by 100.

Can the accepted value be zero?

No. The relative percent-error formula is undefined for a zero reference.

Percent Error Calculator with Formula and Steps

Compare a measured result with an accepted value and see how far off it is as a percentage.

Quick Answer

Experimental 48 vs. accepted 50 gives 4% error. The absolute difference is 2; 2 ÷ 50 × 100 = 4%.

Percent error = |experimental − accepted| ÷ |accepted| × 100%

Absolute percent error

The measurement is 2 below the accepted value.

Absolute difference2

Signed difference−2

Steps

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How to Use the Percent Error Calculator

Enter your measured result and the accepted reference value in the same units. The tool subtracts them, takes the absolute difference, divides by the magnitude of the accepted value, and multiplies by 100. The result is always nonnegative.

Percent Error Formula

Percent error measures the size of a measurement’s deviation relative to the accepted value. The absolute value bars keep the reported error nonnegative. The signed difference is shown separately so you can see whether the measurement was higher or lower.

% error = |measured − accepted| / |accepted| × 100

Worked Example: 48 Compared with 50

Subtract: 48 − 50 = −2. Take the absolute difference: |−2| = 2. Divide by the accepted value: 2 ÷ 50 = 0.04. Convert to a percentage: 0.04 × 100 = 4%.

Percent Error vs. Percent Change

Percent error compares a measured value with a known or accepted reference. Percent change compares an old value with a new value over time. They can use different denominators and answer different questions. Use percent change for growth or decline, and percent error for measurement accuracy.

What If the Accepted Value Is Zero?

The standard relative percent-error formula would divide by zero, so it is undefined when the accepted value is 0. Report the absolute difference instead, or use the method required by your lab or course.

Percent Error FAQs

Can percent error be negative?

The absolute percent error shown here cannot be negative; the signed difference can be.

Is a larger percent error better?

A smaller percent error means the measurement is closer to the accepted reference.

Is percent error the same as percent difference?

No. Percent difference often compares two peer measurements using their average in the denominator.

Editorial review

SolverCalc names Prof. Dr. Khalil Mudassar as its educational reviewer. The formulas and examples are documented in the references below.

Sources

View references

Disclaimer

For educational use. Check your class or textbook convention when the problem defines a different range, sequence index, or notation.