Percent Error Calculator.
Experimental is lower than theoretical by 0.01.
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Browse allWhat Is Percent Error?
Percent error measures how far an experimental (observed) result is from an accepted or theoretical value. Scientists and students use it in chemistry, physics, and biology labs to report measurement accuracy.
Lower percent error means your measurement is closer to the expected value.
How to Use This Calculator
- Enter your experimental (measured) value.
- Enter the theoretical (accepted) value from your textbook or lab manual.
- Review percent error, absolute error, and relative error instantly.
- Note whether your result was higher or lower than expected for your lab report.
Percent Error Formula
Absolute error = |Exp − Theo| · Relative error = |Exp − Theo| / |Theo|
Worked Example
You measure gravitational acceleration as 9.8 m/s² (experimental) and the accepted value is 9.81 m/s² (theoretical).
Absolute error = |9.8 − 9.81| = 0.01
Relative error = 0.01 / 9.81 ≈ 0.001019
Percent error = 0.001019 × 100 ≈ 0.10%
The experimental value is slightly lower than theoretical — a very small error for a classroom lab.
Frequently Asked Questions
How do I calculate percent error?
Subtract theoretical from experimental, take the absolute value, divide by |theoretical|, then multiply by 100. Formula: |Exp − Theo| / |Theo| × 100.
What is the percent error formula?
Percent error = |experimental − theoretical| / |theoretical| × 100. Absolute error = |Exp − Theo|; relative error = absolute error ÷ |Theo|.
Can percent error be negative?
Standard percent error uses absolute values, so it is always non-negative. This calculator separately notes whether your experimental value was higher or lower than theoretical.
What if the theoretical value is zero?
Percent and relative error are undefined (division by zero). Absolute error can still be calculated as |experimental − 0|.
What is a good percent error in a lab?
It depends on the experiment. Many intro labs consider under 5% excellent and under 10% acceptable. Check your instructor's rubric for specific thresholds.
What is the difference between absolute and relative error?
Absolute error is the raw difference |Exp − Theo|. Relative error divides that by the theoretical value, showing error as a fraction of the expected result.
When do I use percent error vs percent difference?
Use percent error when comparing a measurement to a known accepted value. Use percent difference when both values are experimental with no accepted standard.
Which value goes on top — experimental or theoretical?
The difference is |experimental − theoretical|, but you always divide by the theoretical (accepted) value — never by the experimental result.
Percent error is a quick way to show how close your lab work came to the expected result. Use this free calculator for fast numbers, then explain any large errors with equipment limits, rounding, or experimental conditions.