📐 Uncertainty Calculator
Estimate the uncertainty of a measurement’s mean value using standard deviation, sample size, and your chosen confidence level.
What is measurement uncertainty?
Measurement uncertainty describes the range within which the true value of a measured quantity is expected to fall, given the variability observed across repeated measurements and the chosen confidence level.
The formula
Uncertainty = z × (s / √n), where s is the standard deviation of your measurements, n is the number of measurements, and z is the critical value for your chosen confidence level (1.645 for 90%, 1.96 for 95%, 2.576 for 99%, assuming a roughly normal distribution). The result is added to and subtracted from the mean to get the uncertainty range.
This calculator provides a general statistical estimate for planning and educational purposes; formal metrology and laboratory work may require more detailed combined-uncertainty budgets following documents such as the GUM (Guide to the Expression of Uncertainty in Measurement).