Latent Heat of Phase Change Calculator
Find the energy needed to melt, freeze, boil, or condense a substance using the latent heat relation Q = mL.
Solve for
Latent heat preset
kg
Equivalent to 167 kJ
- 1
Latent heat L
334,000 J/kg - 2
Mass m
0.5 kg - 3
Heat energy Q = m × L
0.5 × 334,000 = 167,000
How does this calculator work?
Latent heat is the energy for a phase change at constant temperature, given by Q = m·L. Multiply the mass in kilograms by the specific latent heat (J/kg) of fusion or vaporization to get the heat Q in joules. Rearrange to m = Q/L or L = Q/m to solve for mass or latent heat.
Formula
How this is calculated
A phase change (solid to liquid, or liquid to gas) absorbs or releases energy without changing temperature. The heat involved is Q = m·L, where m is the mass in kilograms and L is the specific latent heat in joules per kilogram. Latent heat of fusion applies to melting and freezing, while latent heat of vaporization applies to boiling and condensation; for water these are about 3.34×10^5 J/kg and 2.26×10^6 J/kg respectively.
Choose what to solve for and the calculator rearranges the same equation: Q = m·L to find the heat, m = Q/L to find the required mass, or L = Q/m to find the implied latent heat. Pick a preset for water or enter a custom L for any material. The result is reported in joules and kilojoules (1 kJ = 1000 J).
The model assumes the substance is already at its transition temperature, so no sensible heating (mcΔT) is included, and that the full phase change occurs. Divide-by-zero cases (L = 0 when solving for mass, or m = 0 when solving for L) return no result. Use consistent SI units: mass in kg, L in J/kg, and Q in J.
Frequently asked questions
Fusion is the energy per kilogram to change between solid and liquid (melting or freezing); vaporization is the energy per kilogram to change between liquid and gas (boiling or condensing). Vaporization is usually much larger.
No. Latent heat covers the phase change at a constant transition temperature. To also heat or cool the substance, add the sensible heat Q = m·c·ΔT separately.
Keep units consistent. If you enter mass in kilograms and L in J/kg, Q comes out in joules. Convert grams to kilograms (divide by 1000) before entering, or scale L accordingly.
Also known as
TG we-Calculate Editorial Team. (2026). Latent Heat of Phase Change Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/latent-heat-calculator
TG we-Calculate Editorial Team. "Latent Heat of Phase Change Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/latent-heat-calculator.
TG we-Calculate Editorial Team, "Latent Heat of Phase Change Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/latent-heat-calculator
@misc{wecalculate_latent_heat_calculator, title = {Latent Heat of Phase Change Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/latent-heat-calculator}}, year = {2026}, note = {TG we-Calculate} }
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