Freezing Point Depression Calculator
Enter the molality, the van 't Hoff factor, and the solvent (or a custom cryoscopic constant Kf) to find the freezing-point depression. Optionally get the estimated freezing point of the solution. This is an idealized dilute-solution model.
Last updated: September 26, 2026
Frequently asked questions
What is freezing-point depression?
It's the decrease in a solvent's freezing temperature when a nonvolatile solute is dissolved in it. Dissolved particles interfere with the solvent's ability to form an ordered solid, so a lower temperature is needed to freeze.
What is the formula?
ΔTf = i × Kf × m, where i is the van 't Hoff factor, Kf is the solvent's cryoscopic constant in K·kg/mol, and m is the molality in mol/kg.
How is this different from Boiling Point Elevation?
Both are colligative properties from the same dissolved-particle effect, but freezing-point depression lowers the freezing temperature while boiling-point elevation raises the boiling temperature. Each solvent has its own separate Kf and Kb constants, which are generally different from each other.
What van 't Hoff factor should I use?
About 1 for molecules that don't dissociate, like sugar, and close to 2 for a fully dissociated salt like NaCl. Real solutions deviate from these ideal values, especially at higher concentrations.
Why does Kf differ for each solvent?
Kf depends on the solvent's molar mass and enthalpy of fusion. That's why the calculator offers solvent presets and a custom option instead of one constant for everything.
When does the equation become unreliable?
For concentrated, strongly interacting, or highly nonideal solutions. It's an idealized model best suited to dilute solutions.