Free Normal Distribution Calculator - Calculates the probability that a random variable is less than or greater than a value or between 2 values using the Normal Distribution z-score (z value) method (Central Limit Theorem).

Also calculates the Range of values for the 68-95-99.7 rule, or three-sigma rule, or empirical rule. Calculates z score probability

This calculator has 4 inputs.

Also calculates the Range of values for the 68-95-99.7 rule, or three-sigma rule, or empirical rule. Calculates z score probability

This calculator has 4 inputs.

- distribution
- value range for a variable
- empirical rule
- Provides estimate for the spread of data in a normal distribution. 68% of the data will fall within one standard deviation of the mean. 95% of the data will fall within two standard deviations of the mean. 99.7% of the data will fall within three standard deviations of the mean
- event
- a set of outcomes of an experiment to which a probability is assigned.
- mean
- A statistical measurement also known as the average
- normal distribution
- an arrangement of a data set in which most values cluster in the middle of the range and the rest taper off symmetrically toward either extreme.
- probability
- the likelihood of an event happening. This value is always between 0 and 1.

P(Event Happening) = Number of Ways the Even Can Happen / Total Number of Outcomes - standard deviation
- a measure of the amount of variation or dispersion of a set of values. The square root of variance
- variance
- How far a set of random numbers are spead out from the mean
- z score
- the number of standard deviations from the mean a data point is. Also known as a standard score