About the Poisson Distribution Calculator
A free tool for finding Poisson probabilities from an average rate.
What it is
This calculator computes P(X=k), P(Xโคk), and P(Xโฅk) for a Poisson-distributed random variable given the average rate ฮป, and plots the full probability distribution as a bar chart around your chosen k value.
Features
Three probability types
Exact, at-most, and at-least probabilities together.
Distribution chart
Visualize the shape of the distribution around k.
Mean and variance
Both equal ฮป, shown alongside the probabilities.
Instant, private
Runs entirely in your browser. No data is sent anywhere.