Z Score

How to use this calculator

1. Enter observation in number.
2. Enter mean in number.
3. Enter standard deviation in number.
4. Select Calculate and keep the output unit with the answer.

Before you use the answer

Choose the reference quantity before interpreting the number. A ratio, a percentage and a percentage-point difference may use the same observations while answering different questions. For recorded data, keep the original values beside the summary so an unexpected result can be traced back to its inputs.

A z score alone does not establish a probability. Probability interpretation needs a distributional assumption.

Does it save my inputs?

No calculation history is stored by this website. The calculator works locally in your browser. See the privacy policy for hosting and contact details.

Why might a result be approximate?

Measurement uncertainty, ideal-model assumptions and floating-point rounding can all matter. Displaying more digits does not improve the original measurement.