Science Fair Measurement Calculator

Work out science fair measurement instantly with clear inputs, formula shown and shareable results.

About Science Fair Measurement Calculator

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.

Formulas

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

Worked example

With the default values below, Science Fair Measurement Calculator returns Mean of the readings of 12.1800. Change any input above and every figure here is recalculated in your browser.

Inputs used

Measurements (comma separated): 12.1, 12.4, 11.9, 12.3, 12.2
Accepted or true value: 12.2

Results

Mean of the readings: 12.1800
Sample standard deviation: 0.1924
Percent error against the true value: 0.164%
Range (highest minus lowest): 0.5000

Step by step

1Values used
2Mean and spread
3Percent error
4Mean of the readings= 12.1800
5Sample standard deviation= 0.1924
6Percent error against the true value= 0.164
7Range (highest minus lowest)= 0.5000

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Science Fair Measurement figure worked out?

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.

Why does this matter?

Accuracy and precision are different claims: a tight standard deviation with a large percent error means a consistent but wrongly calibrated instrument.

What do I need to enter?

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.