Normal CDF Calculator
Calculate the standard normal cumulative distribution probability for a z-score.
Formula and assumptions
Uses a numerical approximation to the normal CDF; not exact symbolic arithmetic.
Results depend on the inputs and assumptions shown. Check units and independently verify important decisions.
For general information. Report an issue.
Frequently asked questions
What does CDF mean?
CDF stands for cumulative distribution function. For a normal distribution, it gives the probability that a value is less than or equal to a specified value.
What does a standard normal CDF calculate?
It calculates the area under the standard normal curve to the left of the entered z-score, where the distribution has mean 0 and standard deviation 1.
Can I use a raw score instead of a z-score?
This tool expects a z-score. Convert a raw value using z = (x − mean) / standard deviation before entering it.