This work evaluates some of the methods that exist to predict the expansion of granular filter media during the backwashing. Basically they were considered three methods, the Classic Method, the more used, allows to know in a quick and simple way the value of the expansion; the second, Sholji’s Method, more elaborated mathematically, predicts the expansion starting from a lineal adjustment among the expansion and the backwashing velocity; and the third, Dharmarajah and Cleasby’s Method, adjusts by means of an equation, two parameters that depend fundamentally on the initial porosity and of the backwashing velocity. To evaluate these methods single sand or anthracite media and double sand and anthracite media were used, which completed with the requirements demanded by the RAS-2000. The results obtained for the single and double standard media are presented. The results obtained for each one of the methods are quite satisfactory, with prediction errors that don’t overcome 10% in none of the analyzed cases.