# Percent Error Calculator

Calculate percent error between experimental and theoretical values instantly. Free online percent error calculator for science, chemistry, and physics.

## What this calculates

Calculate the percent error between your experimental result and the accepted theoretical value. This tool is essential for science labs, chemistry experiments, and physics calculations where you need to quantify measurement accuracy.

## Inputs

- **Experimental (Measured) Value** — The value obtained from measurement or experiment.
- **Theoretical (Accepted) Value** — The known, accepted, or true value.

## Outputs

- **Percent Error** — The percent error between experimental and theoretical values.
- **Absolute Error** — The absolute difference between experimental and theoretical values.
- **Relative Error** — The ratio of absolute error to the theoretical value.

## Details

Percent error quantifies how far an experimental measurement deviates from the true or accepted value. The formula is: Percent Error = |Experimental - Theoretical| / |Theoretical| x 100. The result is always a non-negative number expressed as a percentage.

Related concepts include absolute error (the raw difference between values) and relative error (the ratio of absolute error to the theoretical value, expressed as a decimal). Percent error is simply the relative error multiplied by 100.

In laboratory settings, percent error helps evaluate the quality of an experiment. A low percent error indicates that the experimental method is accurate, while a high percent error may suggest systematic errors, equipment limitations, or procedural mistakes. For example, if a chemistry experiment yields a boiling point of 99.1 degrees C and the accepted value is 100.0 degrees C, the percent error is |99.1 - 100.0| / 100.0 x 100 = 0.9%.

## Frequently Asked Questions

**Q: What is the formula for percent error?**

A: Percent Error = |Experimental Value - Theoretical Value| / |Theoretical Value| x 100. The numerator is the absolute difference between the two values, and the denominator is the absolute value of the accepted theoretical value.

**Q: Can percent error be negative?**

A: The standard percent error formula uses absolute values, so the result is always non-negative. However, some fields use a signed version (without absolute value in the numerator) to indicate whether the experimental value is above (+) or below (-) the theoretical value.

**Q: What is the difference between absolute error and relative error?**

A: Absolute error is the raw difference: |Experimental - Theoretical|. Relative error divides the absolute error by the theoretical value, giving a dimensionless ratio. Percent error is the relative error expressed as a percentage (multiplied by 100).

**Q: What is considered an acceptable percent error?**

A: Acceptable percent error depends on the field. In introductory physics labs, 5-10% may be acceptable. In analytical chemistry, errors below 1% are often expected. In precision manufacturing, tolerances can be much tighter. Always check the requirements for your specific application.

**Q: What if the theoretical value is zero?**

A: When the theoretical value is zero, the percent error formula involves division by zero and is undefined. In such cases, use absolute error instead, or consider an alternative metric like mean absolute error for evaluating the measurement.

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Source: https://vastcalc.com/calculators/math/percent-error
Category: Math
Last updated: 2026-04-21