Compare a measured value with the true value to see how far off it is as a percentage, with the working shown.
Percent error shows how far a measured, or observed, value is from the true value, as a percentage of the true value. It is used in science classes and labs to judge how good a measurement is. A small percent error means the measurement is close to the accepted value, and a large one suggests a mistake in the method or the equipment.
Subtract the true value from the observed value, divide by the true value, and multiply by 100. The result is negative when the observed value is lower than the true value and positive when it is higher. Many textbooks take the absolute value so the error is always positive, since only the size of the error matters. The calculator shows both the signed error and the absolute error.
Say you measure a length as 56.891 and the true length is 62.327. The difference is 56.891 minus 62.327, which is negative 5.436. Divide by 62.327 to get negative 0.0872, and multiply by 100 for a percent error of negative 8.72%. As an absolute value, the measurement is off by 8.72%. If the true value is zero, percent error cannot be worked out, because you cannot divide by zero.
Take the observed value minus the true value, divide by the true value, and multiply by 100. Many classes use the absolute value of the result.
Yes, if you do not take the absolute value. A negative result means the observed value is smaller than a positive true value.
A smaller one is better. Below about 5% is often seen as good in school labs, but what is acceptable depends on the experiment.
Percent error is undefined, since it would mean dividing by zero. Use the absolute error instead.
Percent error compares a measurement with a known true value. Percent difference compares two values when neither is the true one.
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