Percent Error Calculator

Find the percent error between a measured value and the accepted value, with the absolute and signed error.

Formula explained below

What you measured or calculated

The known or theoretical value. It cannot be 0.

Percent error

9.2593%

Absolute error
0.25
Signed error (negative means below)
-9.2593%

A measured value of 2.45 against an accepted value of 2.7 is a percent error of 9.26%.

Calculation breakdown

StepFormulaResult
Absolute error|2.45 − 2.7|0.25
Percent error0.25 ÷ 2.7 × 1009.2593%

How it works

Enter the value you measured and the accepted value.

Percent error = |Experimental value − Accepted value| ÷ |Accepted value| × 100%Signed error = (Experimental value − Accepted value) ÷ |Accepted value| × 100%

Worked example

An aluminum density measured as 2.45 g/cm³, where the accepted value is 2.70 g/cm³:

  1. Absolute error: |2.45 − 2.70| = 0.25
  2. Percent error: 0.25 ÷ 2.70 × 100 = 9.26%
  3. Signed error: −9.26%, because the measurement is below the accepted value

Rounding

The percent error is shown to four decimal places. Calculations use the unrounded values.

Sources

Frequently asked questions

How do you calculate percent error?

Subtract the accepted value from the experimental value, take the absolute value, divide by the accepted value and multiply by 100. For an experimental density of 2.45 g/cm³ against the accepted 2.70 g/cm³ for aluminum, that is 0.25 ÷ 2.70 × 100 = 9.26%.

What is the difference between percent error and percent change?

Percent error compares a measurement with a known, accepted value, so the accepted value is the base. Percent change compares a new value with an old one, so the old value is the base. The percentage calculator on this site handles percent change.

Can percent error be negative?

The usual percent error is always zero or positive because it uses the absolute value. The calculator also shows a signed error, which is negative when your measured value is below the accepted one and positive when it is above.

Can percent error be more than 100%?

Yes. If your measurement is more than double the accepted value, or is on the other side of zero, the error is greater than 100%. A large percent error usually points to a mistake in the measurement or a wrong unit.

Why can the accepted value not be zero?

Percent error divides by the accepted value, and division by zero has no result. If the true value is zero, report the absolute error instead.

PercentagePercentage of, change & differenceStandard ErrorSE of the mean and confidence intervalCoefficient of VariationCV as a percentage of the meanFractionAdd, subtract and simplify

For information only. Percent error assumes the accepted value is the true or reference value.