Percentage Error Calculator
Calculate the percentage error and absolute error between a measured and true value.
% Error = |Experimental − Theoretical| / |Theoretical| × 100%
What Is the Percentage Error Calculator?
The Percentage Error Calculator measures how close an experimental or measured value is to the accepted theoretical or true value. It is widely used in science labs, engineering, and quality control to evaluate measurement accuracy and instrument precision.
Formula
How to Use
Enter the experimental (measured) value and the theoretical (accepted or true) value. The calculator computes the absolute difference, divides by the theoretical value, and multiplies by 100 to give the percentage error. A lower percentage indicates a more accurate result.
Example Calculation
You measure the boiling point of water as 98.6°C; the accepted value is 100°C. % Error = |98.6 − 100| ÷ |100| × 100 = 1.4 ÷ 100 × 100 = 1.4%. Your measurement is 1.4% below the true value.
Understanding Percentage Error
Percentage error is a fundamental concept in experimental science and metrology. It quantifies how far off a measurement is from the accepted true value, expressed as a percentage of that true value. A small percentage error indicates high accuracy; a large one signals systematic error in measurement technique or instrument calibration.
The formula uses the absolute value of the difference to ensure the result is always positive (unless you intentionally use signed error to detect bias direction). The denominator is always the theoretical value — not the experimental one — which is what distinguishes percentage error from percentage difference.
Scientists, engineers, and students use percentage error to evaluate laboratory experiments, calibrate instruments, validate simulations against physical measurements, and assess manufacturing tolerances. Bookmark this calculator for quick lab report calculations and quality control checks.
Frequently Asked Questions
What does percentage error tell you?
Percentage error quantifies the accuracy of a measurement relative to the true value. A small percentage error (close to 0%) means your measurement is very accurate.
Is percentage error always positive?
The absolute value formula makes percentage error always non-negative. However, signed error (without absolute value) tells you whether your measurement was too high or too low.
What is an acceptable percentage error in experiments?
It depends on the field. In many school experiments, less than 5% is acceptable. In precision engineering or scientific research, errors below 1% or even 0.1% may be required.
What is the difference between percentage error and percentage difference?
Percentage error compares to a known true value. Percentage difference compares two measurements without assuming one is "correct": |A−B| / ((A+B)/2) × 100.
Is this calculator free?
Yes, completely free with no sign-up needed.
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