Question 1

What is the percent error formula?

Accepted Answer

Percent error = |experimental - theoretical| / |theoretical| × 100%. The absolute values ensure the result is always non-negative, showing how far off your measurement is from the accepted value.

Question 2

Can percent error be negative?

Accepted Answer

By standard convention percent error is reported as a positive number because of the absolute value bars in the formula. If you want the sign to indicate direction (over vs under the accepted value), drop the absolute value to get percent difference with sign.

Question 3

What is a good percent error?

Accepted Answer

It depends on the experiment. In many school labs under 5% is considered good, while precision engineering may require under 0.1%. Anything close to 0% means your experimental value matches the accepted value.

Question 4

Why is my percent error so high?

Accepted Answer

Common causes include measurement instrument limitations, human error reading instruments, uncontrolled environmental factors, calibration issues, or using an incorrect accepted (theoretical) value for comparison.