The cryoscopic constant, also known as the freezing point depression constant, is used to calculate the depression in freezing point when a solute is added to a solvent. The SI unit of the cryoscopic constant is:
\[
\text{K} \cdot \text{kg/mol}
\]
This unit corresponds to the change in freezing point per unit molality (moles of solute per kilogram of solvent).