Math
Percent Error Calculator
Use this percent error calculator for chemistry, physics, and lab reports when you need to compare a measured value with an accepted or theoretical value.
The measured or observed value.
The true, expected, or reference value.
Try an example
Result
Percent error
—
- Absolute error
- —
- Signed error
- —
Student quick launch
Grade planning, algebra checks, and formulas students reach for most.
Study path
Use this calculator with
Follow these when you want the formula behind the answer, a short lesson, or nearby tools in the same topic.
What the percent error calculator solves
Use this percent error calculator for chemistry, physics, and lab reports when you need to compare a measured value with an accepted or theoretical value.
Formula
How to use it
- Enter the measured value from the experiment.
- Enter the accepted or theoretical value.
- Read the percent error and the raw error difference.
How to read the answer
A smaller percent error means the measurement is closer to the accepted value. The signed error tells you whether the measurement was high or low.
Common mistakes and edge cases
- Do not divide by the experimental value unless your teacher specifically asks for percent difference.
- The accepted value cannot be zero in the usual percent error formula.
- Use How far a number sits from zero, so the answer is never negative. for percent error, but keep signed error when direction matters.
Worked examples
Lab value slightly low
Percent error
2%
Measured value high
Percent error
4%
Frequently asked questions
Can percent error be negative?+
Percent error is usually reported as a nonnegative percentage because it uses absolute error. The signed error can be negative when the measured value is low.
What is a good percent error?+
It depends on the experiment. In many classroom labs, a lower percent error is better, but the expected tolerance depends on equipment and method.
About this calculator
- Written by
- mathcheck editorial team
- Last reviewed
- May 8, 2026
Method
- Uses the values entered by the user and stable formulas documented on the page.
Related calculators
Percentage Calculator
Calculate percent of a number, part-to-whole percentages, percent change, missing wholes, and reverse percent changes.
Percentage Change Calculator
Find percentage increase or decrease between an original value and a new value with signed change, absolute change, and steps.
Scientific Notation Calculator
Convert regular numbers to scientific notation and show coefficient, exponent, and engineering notation.
Adding Fractions Calculator
Add up to five fractions or mixed numbers. Finds the least common denominator with prime factors, rewrites each fraction, adds, simplifies, and shows the mixed-number and decimal forms with a fraction-strip picture.
Area Calculator
Find the area of 11 shapes — rectangle, square, triangle (base-height, three sides, or SAS), circle, trapezoid, parallelogram, rhombus, ellipse, regular polygon, sector, and kite — with the formula, substitution, square-unit labels, and a diagram.
Binary Calculator
Add, subtract, multiply, or divide binary numbers with the column method shown: carries, borrows, partial products, and a long-division tableau, plus decimal, hex, and octal equivalents.
Last updated: May 8, 2026