Scientific, information & consultancy services for the food industry

Calculator for determining the probability of detecting a uniformly distributed pathogen in a food

This calculator uses the Poisson Distribution to calculate the probability of at least one sample being positive for a pathogen.

Concentration of pathogen (CFU / Kg or L)

Number of samples
Weight of sample, g



NOTE! Pathogens are often not distributed uniformly in foods and the results obtained should be regarded with caution. No account has been taken of plating efficiency of pathogens on growth media which will lower the probability of detection further. The mathematics behind this calculator are described in the article on sampling.

How to cite this article

Mullan, W.M.A. (2015) [On-line] UK: Available: Accessed: