Kurtosis Calculator

This kurtosis calculator works out the excess kurtosis of any data set, a statistic that tells you how heavy or light the tails of your distribution are compared with a normal (bell curve) distribution, and therefore how likely extreme values are to turn up. Type or paste your numbers into the data set field as a comma separated list, and the calculator instantly returns three figures: the excess kurtosis itself, the mean of your data, and the sample size it used. Excess kurtosis reads as zero for a perfectly normal distribution. A positive result, called leptokurtic, means your data has heavier tails and more outliers than normal, so extreme values are more likely than a bell curve would suggest. A negative result, called platykurtic, means lighter tails and a flatter, more evenly spread shape, with fewer extreme outliers. This matters most in finance, where heavy tails signal higher risk of large losses or gains, and in quality control and research, where it flags whether a process or sample behaves as expected or throws up unusually frequent extremes. Enter at least two values to get a result; the calculator recalculates live as you edit the list. Below you will find the underlying formula, a worked example, and answers to common questions about what the result means.

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