Methods to model the dimensional variation into computer based simulations by the use of error propagation, random sampling and principle component analysis (PCA) and quantify the variations in their functionalities are discussed. Quantifying these functionalities is important in case of rotating equipment like fan blades of aircraft engine or compressor blades of an automobile turbocharger. This paper takes the example of a blade under impact loading and the maximum permanent deformation as the measure of damage quantifies the variation in damage due to manufacturing variations. Three approaches are discussed namely, error propagation, random sampling and constructing a maximum and minimum variance models using single value decomposition techniques like principle component analysis(PCA). Ten blades of same design are considered with their dimensional variations due to manufacturing tolerances. Finite element model of these blades are developed along with variations in the thickness of the blade due to manufacturing variations. Simulations are carried out on these ten blades with different thickness values for impact loading. All the three methodologies of damage quantifications namely error propagation, random sampling and PCA are applied and benefits and draw backs of each method are discussed. © 2017 Elsevier Ltd.