Latent Heat Calculator

About this calculator

This calculator finds the heat energy Q absorbed or released during a phase change — melting, freezing, boiling, or condensing — using the equation Q = m · L, where m is mass and L is the substance's specific latent heat (of fusion or vaporization) in J/kg. Unlike sensible heat, this energy changes a substance's state without changing its temperature, which is why an ice cube stays at 0°C while it melts.

Latent heat values are tabulated for common substances — water's latent heat of fusion is about 334 kJ/kg and its latent heat of vaporization about 2,260 kJ/kg — and the calculation underlies refrigeration and HVAC system design, steam boiler sizing, calorimetry experiments, and industrial processes like metal casting and food freezing.

Mechanical and chemical engineers, HVAC technicians, physics students working through thermodynamics problems, and food scientists calculating freezing loads all rely on this formula. Enter the mass and select a substance or enter its latent heat value to get the total energy required.