Abstract: The centreline runout (a) and out of roundness (b) of a shaft (100) is measured by measuring the distance between the central longitudinal axis (102) of the shaft (100) and each of a plurality of angularly spaced measurement points (103) located on the outer surface of the shaft in a measurement plane (18) using a measuring device (10). The position of the centroid (104) of the shaft at the measurement plane (18) is calculated along with the distance between the centroid (104) and the shaft central longitudinal axis (102), providing a centreline runout measurement (a). The distance between each measurement point (103) and the centroid (104) is calculated with these distances being used to calculate an out of round measurement (b).