Percent Error Calculator
Calculate percent error between experimental and theoretical values.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Enter the experimental (measured) value and the theoretical (accepted) value. The calculator applies the formula: percent error = |experimental - theoretical| / |theoretical| x 100. Results appear instantly as you type.
This tool is commonly used in science labs and physics classes to evaluate how close an experimental measurement is to a known or accepted value.
About Percent Error
Percent error quantifies how far an experimental measurement deviates from a known theoretical value, expressed as a percentage. It is always non-negative because the formula uses absolute values. A lower percent error indicates higher measurement accuracy. This metric is standard practice in chemistry, physics, and engineering for evaluating experimental results.
Frequently Asked Questions
What is a good percent error?
It depends on the experiment. In introductory physics labs, under 5% is generally acceptable. Precision instruments may require under 1%. The acceptable range depends on the equipment and methodology used.
Can percent error be negative?
The standard formula uses absolute values, so the result is always positive or zero. Some fields use a signed version (without absolute value) to indicate direction of error, but this calculator uses the standard unsigned formula.
What if the theoretical value is zero?
Percent error is undefined when the theoretical value is zero because it requires division by the theoretical value. In that case, use absolute error or relative difference instead.