In the analyses of several thousand water samples the author has worked out a series of factors relating conductance to total cone, of dissolved electrolytes. The values of these factors fluctuate chiefly with changes in total electrolyte content and with the percentages of Na+ and of Cl as of total cations and anions respectively. Having detd. the conductance of a water and its Na and Cl content, one can, with the factors presented, calculate with considerable accuracy the total electrolyte content of a water and the sum of Ca + Mg expressed as milli-equivalents. The method here descr. is not offered as a substitute for complete analysis but rather as a means of detecting errors made either in the course of such analyses or in calculating and recording the results. Where a rough estimate of Ca + Mg is all that is needed, the method is satisfactory, provided important amts. of bases other than Ca, Mg, and Na are absent.