Empirical Rule Calculator

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Mean

Standard Deviation

About This Rule

What Is the Empirical Rule?

The empirical rule (also called the 68–95–99.7 rule) describes how data spreads out in a normal distribution: almost all of it falls within 3 standard deviations of the mean, and most of it falls much closer than that.

When to Use It

Quickly estimating what range most of your data falls into, given a mean and standard deviation
Sanity-checking whether a data point is unusually far from the mean
Teaching or visualizing how spread relates to the normal distribution

Worked Example

IQ scores have a mean of 100 and a standard deviation of 15.

68% of people score between 85 and 115
95% of people score between 70 and 130
99.7% of people score between 55 and 145

Your Results

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