How it works
Express how many standard deviations an observation lies above or below a mean. Standard deviation must be positive.
z = (x−μ)/σ
Worked example
Show example inputs and result
Observation: 85 · Mean: 70 · Standard deviation: 10.
- Result
- 1.5
Questions and answers
Why are some results rounded?
Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.
Are my inputs sent to a server?
The calculator processes inputs in your browser. Its code does not send your values to a server.
Method reviewed: October 8, 2026 · Methods & accuracy