A device for characterizing a fire comprises at least one stereovision system and at least one processing unit. The at least one stereovision system comprises a first and a second image capture unit. The at least one processing unit is configured to determine at least one geometric characteristic of the fire. The processing unit is also configured to determine a radiative flux of this fire on the basis of a calibrated linear relationship established between a radiative flux of a reference fire as a function of at least one of the geometric characteristics of the fire and of at least one fire category in order to be able to determine zones exposed to a radiative flux that exceeds a reference threshold. The present disclosure also relates to a method for determining radiative fluxes that implements such a fire characterizing device.