Cone calorimeter is one of the basic test bench for fire behaviour tests on materials. It is used to measure heat release rate of materials under heat flux by thermochemical method. This method is complex and uses a large number of parameters. Test method is nowadays standardized and some of measured parameters are used for material ranking in some regulations. It is therefore essential to determine test bench uncertainty. This paper presents uncertainty calculation applied to the test method and an example of it application to a set of fire behaviour tests on a material.