,

where is Boltzmann's constant, is the standard freezing point for water (273K), is the molecular weight of water (18.02 g/mol), is the molality (mol solute/kg solvent), is the enthalpy of fusion for water (6000 J/mol) and is the freezing-point depression constant (1.86). This equation determines the amount of salt needed. The value is displayed numerically and graphically; also shown (in blue) is the amount of salt carried by the truck.