Percent Error Calculator

Measure experimental accuracy by comparing measured and actual values

Percent Error Calculator


Percent error is a standard calculation in chemistry, physics, biology, engineering, and quality‑control work. It compares a measured or experimental value to the actual, accepted, or theoretical value. The result shows how far off the measurement is — not whether it is above or below the true value, but simply the size of the error. This percent error calculator instantly computes the difference and expresses it as a percentage.

What is the measured value, and the actual value?

Measured value: Actual value:    


How percent error works


Percent error compares how close a measurement is to the true value. The formula is:

percent error = 100 × |measured − actual| / |actual|

The absolute value bars ensure the result is always positive. Percent error measures the *size* of the error, not its direction.

Example: Measured value = 12.86, actual value = 14 percent error = 100 × |12.86 − 14| / |14| = 8.14%

This calculation is used in lab reports, experimental analysis, calibration checks, and manufacturing quality control.



Examples of percent error calculations


Example 1: Chemistry experiment
Measured density = 1.18 g/mL Actual density = 1.25 g/mL Percent error = 100 × |1.18 − 1.25| / 1.25 = 5.6%

Example 2: Physics measurement
Measured acceleration = 9.72 m/s² Actual value = 9.81 m/s² Percent error = 0.92%

Example 3: Biology concentration test
Measured concentration = 2.4% Actual concentration = 2.0% Percent error = 20%

Example 4: Manufacturing tolerance
Measured diameter = 19.7 mm Actual specification = 20.0 mm Percent error = 1.5%

These examples show how percent error applies to laboratory experiments, scientific measurements, industrial processes, and calibration tasks.



Why percent error is useful


Percent error helps evaluate:

  • measurement accuracy
  • instrument reliability
  • experimental technique
  • manufacturing tolerances
  • quality‑control performance

A low percent error indicates a measurement close to the true value. A high percent error suggests experimental mistakes, instrument issues, contamination, or incorrect assumptions.

Percent error is often paired with absolute and relative error to give a complete picture of measurement accuracy.



For more percentage tools — including everyday, math, and scientific calculators — visit our percentage calculator homepage.



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