We present a possibly simple and effective way to identify living specimens of the various species of Nepenthes. The volume and height of the pitchers are closely correlated variables of which the mathematical relationship between them can be expressed in a simple formula. These formulas, preferably of the upper pitchers when available, are slightly different for most species investigated, especially for the largest pitchers on specimens. This method is easily applicable in Botanical Gardens, which generally have a small, highly similar set of species. However, the results are based on few data (few specimens per species, only from two botanical gardens). Thus, please help, by providing more data, especially of hybrids, to further test the method.