To calculate concentricity, the initial thing is to establish a datum and measure all the required features. The datum feature typically consists of a cylindrical or spherical feature that offers a stable reference point. It's recommended to use measurement devices such as a coordinate measuring machine (CMM), laser scanner, or optical comparator to measure the position of the axis or center plane of the cylindrical or spherical feature in relation to the datum axis or center plane. The following formula is used for calculating concentricity: C = (Wmin / Wmax) * 100%. Note: Wmin represents the minimum width, Wmax represents the maximum width, and C is expressed as a percentage. A value of 100% indicates that the tubing is fully concentric.