Z-Score Calculator
Standard score, percentile and tail probabilities.
Enter your values
Results update instantly as you type — no submit needed.
Results
- Z-score
- 2.1333
- Percentile
- 98.36%
- Probability above this value
- 1.645%
- Two-tailed p-value
- 3.2897%
Working
- 1z = (132 − 100) ÷ 15 = 2.1333
Quick answer
A z-score is how many standard deviations a value sits from the mean: z = (x − μ) ÷ σ.
z = (x − μ) ÷ σ
How to use the Z-Score Calculator
- 1Enter the raw value.
- 2Add the population mean and standard deviation.
- 3Read the z-score and percentile.
Frequently asked questions
What z-score is significant?
At the conventional 5% two-tailed level, |z| above 1.96 is significant; 2.58 corresponds to the 1% level.
Can a z-score be negative?
Yes — it simply means the value sits below the mean.