In the first part of this paper we develop analytical equations for short fiber content (SFC), (numerical and weight bases), in terms of the distribution functions used in practice: weight-biased frequency function, staple diagram, and fibrogram. In the second part, the concept of "similar distributions" is introduced and it is demonstrated that SFC can be determined by using a parameter of range (UHM or ML, SL(2.5%), or SL(50%)) and a parameter of shape (UI or UR). Finally, some preliminary results obtained in an attempt to determine statistical models for calculation of SFC from experimental HVI data are discussed. The latter investigation is still in progress.