This paper presents two calibration methods for a CTA probe valid at low speeds covering a range of 0.029 m/s≤U≤1.79 m/s. The well-known in situ calibration method using a simple laminar pipe-flow set-up was used for a mean Re number range of 25≤Re≤1590. The rotating disc method is the proposed calibration method in the speed range of 0.05 m/s≤U≤1.05 m/s. Both calibration methods were compared and found to be in conformity with each other in a maximum error margin of ± 7 %. Therefore derived calibration equation in the form of modified King’s Law with corresponding values of the parameters; A=2.676, B=0.749 and n=0.75 can be utilized at speeds as low as 0.029 m/s with sufficient accuracy.