basic

Poisson Probability Calculator

P(X = k) for a Poisson distribution with mean λ.

Compute the Poisson probability of observing exactly k events when the average rate is λ events per interval.

Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

Inputs

Results

Enter values and click Calculate to see results.
Was this helpful?

How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

P(X = k) = (λᵏ · e⁻λ) / k!

In depth

Compute the Poisson probability of observing exactly k events when the average rate is λ events per interval.