Freezing Point Depression Calculator — Colligative Properties

Calculate freezing point depression using the van't Hoff equation. Find how salt, antifreeze, or any solute lowers the freezing point. Includes molality auto-calculation.

✓ Formula verified: May 2026

Freezing Point Depression

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Cryoscopic Constant (Kf)*Supports both metric (SI) and imperial units. Solvent-specific constant. Water: 1.86, Benzene: 5.12, Camphor: 40, Cyclohexane: 20.2, Acetic acid: 3.90 °C·kg/mol.

°C·kg/mol

Molality (m)*Moles of solute per kilogram of SOLVENT (not solution). For NaCl at 1 mol/kg: m = 1, but i = 2 gives effective 2 mol/kg.

mol/kg

Van't Hoff Factor (i)*Number of particles per formula unit. Non-electrolytes (sugar): 1. NaCl: 2 (Na⁺ + Cl⁻), CaCl₂: 3, MgSO₄: 2. Strong electrolytes: use ideal i. Weak electrolytes: use measured i (lower than ideal).

Solute Mass (optional)Mass of solute added. Optional — enter with solvent mass to auto-calculate molality. For NaCl (MW 58.44): 58.44 g in 1 kg water = 1 molal.

Solvent Mass (optional)Mass of solvent (NOT solution). For a 1 molal NaCl solution: dissolve 58.44 g NaCl in 1,000 g water (total mass ~1,058 g).

Solute Molar Mass (optional)Molar mass of the solute. NaCl: 58.44, CaCl₂: 110.98, Sucrose: 342.3, Ethylene glycol: 62.07 g/mol.

g/mol

Freezing Point Depression (ΔTf)

1.86°C

New Freezing Point

-1.86°C

Formula Used

ΔTf = 1.86 × 1 × 1 = 1.86°C

Effective Molality (m × i)

1 mol/kg

What if your cryoscopic constant (kf) changes? 1.6740000000000002 °C·kg/mol → 1.674°C · 1.86 °C·kg/mol → 1.86°C · 2.0460000000000003 °C·kg/mol → 2.046°C

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