Abstract: By application of the principle of nomography, three nomograms are designed for easy and rapid calculation of isotonic solutions: by means of the first nomogram one can find out the weight of any substance to make any quantity below 100 ml when molecular weight and ionization data of any substance are known; by the second, for calculations based on freezing point depression of 1% solution of the substances, the weight of the substance to make any quantity below 1000 ml is given; the third gives the weights of sodium chloride to adjust solutions of any substance to be isotonic when the freezing-point depression of the solution is known.