An averaging pitot tube is used to measure the thermally induced air flow through the sodium to air heat exchanger used to remove the decay heat generated in the core of a fast breeder reactor after its shutdown. It is practically impossible to calibrate the averaging pitot tube with exact upstream and downstream conditions in the laboratory as in the decay heat removal system. Hence the averaging pitot tube was calibrated experimentally with approximate upstream and downstream conditions and the same was transposed to the site conditions through numerical studies. This paper gives the details of the averaging pitot tube calibration by experiments and numerical method and the comparison between the two methods. The results obtained by both methods were in agreement with a maximum difference of 卤4%in flow coefficient .