Percent Error Calculator

Quickly calculate the percentage error of your experiment to gauge its accuracy. Enter your observed value and the known true value to find the percent error instantly. This essential tool is perfect for students, scientists, and engineers for validating experimental results. Explore more tools on free science calculators on CalculatorBolt.

Enter Values

The value you measured or obtained from your experiment.
The known, accepted, or theoretical value.
True value cannot be zero.

Percent Error = | (Observed - True) / True | × 100%

The absolute value bars | | ensure the result is always positive, representing the magnitude of the error.

Result

Percent Error

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Calculation Steps:

Click calculate to see steps.

How It Works

Percent error is a measure of how inaccurate a measurement is, compared to the true or accepted value. It is calculated by finding the absolute difference between the observed and true values, dividing that by the true value, and then multiplying by 100 to express it as a percentage. The absolute value ensures the error is always a positive number, representing the magnitude of the deviation.

Inputs Explained

  • Observed Value: The value that you actually measured or obtained through your experiment.
  • True Value: The known, correct, or theoretically-accepted value that you are comparing your observation against.

Example

Suppose you are measuring the boiling point of water at sea level. The accepted true value is 100°C, but your experiment records a boiling point of 99.5°C.

  1. Observed Value = 99.5
  2. True Value = 100
  3. Percent Error = | (99.5 - 100) / 100 | × 100
  4. Percent Error = | -0.5 / 100 | × 100
  5. Percent Error = 0.005 × 100 = 0.5%

The percent error of your experiment is 0.5%.

Tips & Notes

  • A lower percent error indicates a more accurate measurement.
  • Percent error is a relative error, meaning it shows the size of the error in relation to the true value.
  • The "true value" can sometimes be an average of multiple measurements or a value from a highly trusted reference source.

FAQs

A "good" or acceptable percent error is highly dependent on the context of the experiment. In some high-precision physics experiments, an error below 1% might be required, while in other fields, 5-10% could be considered acceptable.

The absolute value is used to determine the magnitude or size of the error, regardless of whether the observed value is higher or lower than the true value. This makes the error a positive, non-directional quantity.

Absolute error is the simple difference between the observed and true values (e.g., 0.5°C). Percent error expresses this error as a percentage of the true value, providing a standardized way to compare errors across different scales.

No. The formula for percent error involves dividing by the true value. Division by zero is undefined, so a true value of zero cannot be used in this calculation.

Disclaimer

This calculator provides a mathematical calculation of percent error based on the inputs provided. The interpretation of what constitutes an "acceptable" error depends on the specific scientific context and experimental standards. Always follow the guidelines provided by your instructor or in your field of study.

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Author: CalculatorBolt Editorial Team
Reviewed by: Science Educator
Published: • Updated: