Grain size can be measured using any of the methods outlined in (a) to (e) above. The first two methods (a) and (b) are comparism methods and give results that are within plus or minus a whole grain size and so are not very accurate. The last two methods (d) and (e) are direct measurements but they also give inaccurate result. This is because their parametric reference is just a straight line which when drawn and juxtaposed against a micrograph may lead to much error in counting the number of grains intercepted by the line. At best, therefore, they can only give single parametric description of the grains. This leaves us with that of the planetric Jeffries method (i. e method (c) for the grain size measurement.

This method provides a single number estimate of all the parametric description of grain size mentioned in the introduction. Hence it provides a full description of grain size, which can be used for any structure — property correlation [2]. Before describing the method, it is necessary to present some definitions of grain sizes, which will help us to understand the Jeffries method [1, 2, 2].