Work out science fair measurement instantly with clear inputs, formula shown and shareable results.
The mean averages the repeats, the sample standard deviation uses the n - 1 divisor to measure precision, and percent error compares the mean against the accepted value to measure accuracy. Accuracy and precision are different claims: a tight standard deviation with a large percent error means a consistent but wrongly calibrated instrument.
Mean and spread
mean = sum of readings / count; s = sqrt(sum of (x - mean)^2 / (count - 1))
Percent error
percent error = |mean - true value| / |true value| x 100
mean = sum of readings / count; s = sqrt(sum of (x - mean)^2 / (count - 1)). The mean averages the repeats, the sample standard deviation uses the n - 1 divisor to measure precision, and percent error compares the mean against the accepted value to measure accuracy.
Accuracy and precision are different claims: a tight standard deviation with a large percent error means a consistent but wrongly calibrated instrument.
Enter measurements (comma separated), accepted or true value. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.