Latent Heat Calculator

Latent heat is energy transferred when matter changes phase without changing temperature. During melting, boiling, sublimation, freezing, condensation, or deposition, energy changes the molecular arrangement rather than the average molecular kinetic energy. That is why ice can absorb heat while remaining at its melting point and boiling water can continue absorbing energy while its temperature stays at the boiling point under constant pressure. The governing relationship is Q = m × L. Q is heat energy, m is the mass undergoing the phase change, and L is the specific latent heat for the material and transition. This calculator accepts mass in grams and L in joules per gram, producing energy directly in joules and kilojoules. The sign depends on direction: melting, vaporization, and sublimation absorb energy, while freezing, condensation, and deposition release the same magnitude under equivalent conditions. The calculator reports magnitude so you can apply the appropriate sign in an energy balance. Specific latent heat is not a universal constant for every circumstance. It depends on the substance, transition, pressure, purity, and sometimes temperature. Water near standard atmospheric pressure has a latent heat of fusion of roughly 334 J/g and a latent heat of vaporization near 2260 J/g at its normal boiling point. Reliable design work should use a property table for the actual pressure and operating state rather than a rounded classroom value. Latent heat covers only the phase-change portion of a thermal process. If ice starts below its melting point, energy is first needed to warm the solid to the melting point. After it melts, additional sensible heat raises the liquid temperature. A complete calculation therefore adds each sensible-heating segment, using mass times specific heat capacity times temperature change, and each phase-change segment, using mass times latent heat. This calculation is useful in refrigeration, HVAC, steam systems, cooking, cryogenics, thermal storage, meteorology, chemistry, and physics education. It can estimate the energy needed to melt a material or the heat released when vapor condenses. Real equipment also has heat loss, finite efficiency, changing pressure, and container heat capacity. Include those effects when converting the ideal energy result into heater power, cooling capacity, process time, or operating cost.