🎯 Percent Error Calculator
Compare a measured value to the accepted value: percent error = |experimental − theoretical| ÷ |theoretical| × 100.
Percent error
0.101937%
Signed error
-0.101937%
measured low
Percent error = |experimental − theoretical| ÷ |theoretical| × 100. 🔒 Computed in your browser.
How the percent error calculator works
Percent error measures how far a measurement is from the accepted value: |experimental − theoretical| ÷ |theoretical| × 100. The tool also shows the signed error, indicating whether your measurement came out high or low.
The standard lab metric for accuracy. A small percent error means your measurement is close to the accepted value; the signed version tells you the direction of the discrepancy.
Frequently asked questions
How do you calculate percent error?
Take the absolute difference between the experimental and theoretical values, divide by the absolute theoretical value, and multiply by 100: |exp − theo| / |theo| × 100.
What is a good percent error?
It depends on the experiment, but in student labs under about 5% is often considered good. Lower is better; the acceptable range depends on the equipment and method.
What is the difference between percent error and percent difference?
Percent error compares a measurement to a known accepted value; percent difference compares two measured values with no “correct” reference (dividing by their average).
Can percent error be negative?
The standard percent error uses absolute value, so it is non-negative. This tool also shows a signed error to indicate whether the measurement was too high (+) or too low (−).
Why divide by the theoretical value?
Because the theoretical (accepted) value is the reference standard; the error is expressed relative to it, making it comparable across different scales.