Fiber diameter and its distribution are one of the most important parameters related with the quality of electrospun web. The diameter of electrospun nanofibres is not uniform and the histograms of values are usually distributed differently. Analysis of literature sources showed that sometimes the distribution curves are similar to normal (Gaussian) distribution. Sometimes the distribution shapes are sophisticated and do not resemble this one. The problem arises because it is impossible to compare the average values of different measurement distributions, and a method with possibilities to compare the different results for estimation of nanofibre web quality is necessary. Yet, till now no standardized method for measurement of the diameter and evaluation of the distribution has been created. In this article, various distributions from literature sources and those of nanofibre diameter obtained during own experiments were analysed. Values of the nanofibre diameter are described by normal (Gaussian) and compound mathematical distributions. It was decided that the skew of distribution along with other characteristics can be used as criterion for web estimation and the diameter of nanofibres can be described by skewed normal (Gaussian) distribution when the coefficient of skewness is less than 0.5. The possibilities of estimation by compound distribution from a few normal distributions must be checked when the coefficient is higher: