Kurtosis Calculator

About this calculator

Kurtosis measures how heavy or light the tails of a distribution are compared to its center — in other words, how likely extreme values are relative to a normal distribution. A normal (Gaussian) distribution has a kurtosis of exactly 3, so statisticians usually report excess kurtosis, which is kurtosis minus 3, so that a normal distribution reads as 0. Positive excess kurtosis (leptokurtic) means heavier tails and more outliers than normal, while negative excess kurtosis (platykurtic) means lighter tails and fewer extreme values.

Financial analysts watch excess kurtosis in return distributions because heavy tails mean extreme gains or losses are more likely than a normal-distribution model would predict — a key input for risk management and stress-testing beyond what standard deviation alone captures. Quality-control engineers and researchers fitting statistical models to real data use it the same way, as a check on whether a normal-distribution assumption is safe to use.

Enter a list of numbers and the calculator computes the population kurtosis along with the excess kurtosis, showing how heavy-tailed your data is relative to a normal distribution.