How To Calculate Experimental Error

Chemistry Quick Review of Experimental Error

Error is the accuracy limit of your measurements.
Error is the accuracy limit of your measurements. Ejay, Creative Commons License

Error is a measure of the accuracy of the values in your experiment. It is important to be able to calculate experimental error, but there is more than one way to calculate and express it. Here are the most common ways to calculate experimental error:

Error Formula

In general, error is the difference between an accepted or theoretical value and an experimental value.

Error = Experimental Value - Known Value

Relative Error Formula

Relative Error = Error / Known Value

Percent ErrorĀ Formula

% Error = Relative Error x 100%

Example Error Calculations

Let's say a researcher measures the mass of a sample to be 5.51 g. The actual mass of the sample is known to be 5.80 g. Calculate the error of the measurement.

Experimental Value = 5.51 g
Known Value = 5.80 g

Error = Experimental Value - Known Value
Error = 5.51 g - 5.80 g
Error = - 0.29 g

Relative Error = Error / Known Value
Relative Error = - 0.29 g / 5.80 g
Relative Error = - 0.050

% Error = Relative Error x 100%
% Error = - 0.050 x 100%
% Error = - 5.0%