A simple calibration chart is presented for correlating the Preston tube reading directly with the friction velocity. This chart provides a quick and easy way to obtain the friction velocity (an important scaling velocity in turbulent flow studies) and consequently the wall shear stress. In addition the chart overcomes most of the drawbacks of previous Preston tube calibration methods. A comparison between friction velocities obtained using the chart and the corresponding values obtained from Patel’s calibration shows a good agreement with a maximum difference of 5%.