Math Tools
Percent Error Calculator
Calculate absolute error and percent error between experimental and theoretical values.
Percent Error Calculator
Calculate percent error and absolute error from experimental and theoretical values quickly and accurately.
Formula
Percent Error = |(Experimental - Theoretical) / Theoretical| × 100
Result
Absolute error
0.2
Percent error
2%
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What percent error means
Percent error measures how far an experimental result is from the expected or theoretical value, expressed as a percentage. It is commonly used in science labs, physics, chemistry, engineering, and math to show the size of an error relative to the accepted value.
What is a percent error calculator?
A percent error calculator is a tool that compares an experimental value to a theoretical, accepted, or expected value. It calculates both the absolute error and the percent error so you can see not only the size of the difference, but also how large that difference is relative to the correct value.
This is useful in science experiments, lab reports, classroom assignments, engineering checks, and measurement analysis where accuracy matters. Instead of computing the formula manually, you can enter two numbers and get the answer instantly.
Percent error formula and absolute error formula
Absolute error formula
Absolute Error = |Experimental - Theoretical|
Percent error formula
Percent Error = |(Experimental - Theoretical) / Theoretical| × 100
Absolute error tells you the raw difference between the two values. Percent error goes one step further by showing that difference as a percentage of the theoretical value.
Because the formula uses an absolute value, percent error is usually expressed as a positive percentage.
Percent error examples table
These examples show how to calculate absolute error and percent error for common values.
| Experimental value | Theoretical value | Absolute error | Percent error |
|---|---|---|---|
| 9.8 | 10 | 0.2 | 2% |
| 48 | 50 | 2 | 4% |
| 102 | 100 | 2 | 2% |
| 19.5 | 20 | 0.5 | 2.5% |
Percent error interpretation table
The meaning of a percent error depends on the subject, equipment, and expected accuracy, but this table gives a simple reference for common classroom and measurement situations.
| Percent error | General meaning |
|---|---|
| 0% | Exact match with the theoretical value |
| Less than 1% | Very small error in many classroom or measurement contexts |
| 1% to 5% | Often considered a small error, depending on the experiment |
| 5% to 10% | Moderate error that may need explanation or review |
| More than 10% | Large error that may suggest measurement or method issues |
How to calculate percent error step by step
First, subtract the theoretical value from the experimental value. Then take the absolute value of that difference so the error is expressed as a positive amount.
Next, divide the absolute error by the theoretical value. Finally, multiply the result by 100 to convert it into a percentage. That gives you the percent error.
For example, if the experimental value is 9.8 and the theoretical value is 10, the absolute error is 0.2. Dividing 0.2 by 10 and multiplying by 100 gives a percent error of 2%.
When to use a percent error calculator
A percent error calculator is useful in chemistry, physics, engineering, biology, and statistics whenever you need to compare a measured value with an accepted value. It helps you evaluate how accurate a result is.
Students often use percent error in lab reports and homework, while professionals use it in testing, calibration, and quality control. It is especially helpful when comparing results across different scales because percent error standardizes the difference.
Why percent error is useful
Percent error gives more context than raw error alone. A difference of 2 units may be small in one situation and large in another, depending on the size of the theoretical value.
By converting the error into a percentage, it becomes easier to compare results, judge accuracy, and explain measurement quality in a clear and standardized way.
Percent error calculator FAQ and common questions
What is percent error in simple terms?
Percent error tells you how far your measured or experimental value is from the accepted or theoretical value, shown as a percentage.
How do you find percent error?
Subtract the theoretical value from the experimental value, take the absolute value, divide by the theoretical value, and multiply by 100.
What is the difference between absolute error and percent error?
Absolute error is the raw difference between the two values. Percent error expresses that difference as a percentage of the theoretical value.
Can percent error be negative?
In standard usage, percent error is usually written as a positive value because the formula uses the absolute value of the difference.
Why do scientists use percent error?
Scientists use percent error to judge how close an experimental result is to an accepted value and to compare measurement accuracy across different experiments.
What happens if the theoretical value is zero?
Percent error cannot be calculated when the theoretical value is zero because division by zero is undefined.
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