Is percent error always positive?

Yes. This calculator takes the absolute value of the difference, so the percent error is reported as a positive number regardless of whether the measurement was above or below the accepted value.

What is the difference between absolute error and percent error?

Absolute error is the raw size of the difference between the measured and accepted values, in the original units. Percent error scales that difference relative to the accepted value, so it can be compared across measurements of different magnitudes.

What happens if the theoretical value is zero?

Percent error is undefined when the accepted value is zero because you cannot divide by it. This calculator returns a percent error of 0 in that case and still reports the absolute error so the difference is not lost.

Percent Error Calculator

Experimental Value

Theoretical Value

Percent Error10.00%

Absolute Error1.0000

Percent error measures how far an experimental or measured value lands from a known, accepted, or theoretical value, stated as a percentage of that accepted value. This calculator reports both the absolute error and the percent error, making it a quick check on accuracy in lab work, physics, and engineering measurements.

Formula

percent error = |experimental - theoretical| / |theoretical| × 100

experimental: The value you measured or obtained
theoretical: The accepted, known, or true value

How it works

Enter your experimental (measured) value and the theoretical (accepted or true) value.
The calculator finds the absolute error as the absolute difference between the two, then divides that by the theoretical value and multiplies by 100 to get the percent error. The result is always reported as a positive percentage.

Worked example

A student measures gravitational acceleration as 9.8 m/s² against the accepted value of 9.81 m/s².

Absolute error = |9.8 - 9.81| = 0.01.
Divide by the theoretical value: 0.01 / 9.81 = 0.0010194.
Multiply by 100: 0.0010194 × 100 = 0.10194%.

Percent error ≈ 0.10%, with an absolute error of 0.01 m/s².

Frequently asked questions

Is percent error always positive?: Yes. This calculator takes the absolute value of the difference, so the percent error is reported as a positive number regardless of whether the measurement was above or below the accepted value.
What is the difference between absolute error and percent error?: Absolute error is the raw size of the difference between the measured and accepted values, in the original units. Percent error scales that difference relative to the accepted value, so it can be compared across measurements of different magnitudes.
What happens if the theoretical value is zero?: Percent error is undefined when the accepted value is zero because you cannot divide by it. This calculator returns a percent error of 0 in that case and still reports the absolute error so the difference is not lost.

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