Poisson Probability Calculator
Calculate exact and cumulative Poisson event probabilities.
Use this free online Poisson Probability Calculator to evaluate probabilities for event counts over fixed intervals with known average rate. It is useful for analysis, reporting, coursework, and experiment planning when you need quick statistical evidence without building a spreadsheet. The form focuses on Lambda (expected events), k (event count) and returns Poisson Inputs, Result, so you can move from input to answer without setting up a spreadsheet or custom script. Run one realistic example, adjust the inputs, and compare how the result changes before you copy or share it. Treat the result as a statistical aid: sample quality, independence, distribution assumptions, and context still determine whether the conclusion is valid.