Normal Distribution Calculator
Probabilities under the bell curve.
Enter your values
Results update instantly as you type — no submit needed.
Results
- P(X < x)
- 0.908789
- P(X > x)
- 0.091211
- Z score
- 1.33333
- Percentile
- 90.88%
- P(x < X < x₂)
- 0.068461
Quick answer
The normal distribution converts any value to a z-score, then reads the area under the standard bell curve.
z = (x − μ) / σ
How to use the Normal Distribution Calculator
- 1Enter the population mean and standard deviation.
- 2Enter the value you are testing.
- 3Add a second value for a range probability.
Frequently asked questions
What is the 68-95-99.7 rule?
About 68% of data lies within 1 SD, 95% within 2 and 99.7% within 3.
Is my data normal?
Check a histogram or QQ plot; heavily skewed data needs different tools.