Percent Error Calculator

What percent error measures

Percent error tells you how far an experimental (measured) result is from the theoretical or accepted value, expressed as a percentage of that accepted value. It is one of the most common ways to judge the accuracy of a lab measurement.

The formula

Percent error is calculated as: |Experimental − Theoretical| ÷ |Theoretical| × 100%. A signed version (without the absolute value on the difference) is also shown, which tells you whether your measurement ran high or low.

• A small percent error means your measurement is close to the accepted value.
• A large percent error can point to measurement error, equipment limitations, or an unaccounted-for variable.

Note: This calculator is for general educational and lab-reporting use; it does not diagnose the cause of any discrepancy.