Latent heat converter
Convert latent heat between kJ/kg and BTU/lb — the energy a substance absorbs while changing state without changing temperature.
That's about the same as boiling water. A 2 kW kettle would need about 1,129 seconds to supply that for one kilogram.
What it means
How much energy is that?
Latent heat is quoted at the transition temperature and pressure. Water’s 2,257 kJ/kg is at 100 °C; at 20 °C evaporation costs about 2,450.
Every unit
Your latent heat in every unit
Learn
Three things worth knowing
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Boiling water costs 2,257 kJ/kg
Nearly seven times what it takes to heat the same water from freezing to boiling. Most of a kettle’s energy would go into steam, if you let it.
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Joseph Black, 1762
He noticed ice took hours to melt in a warm room while staying at 0 °C, and concluded the heat was going somewhere invisible. He called it latent — hidden.
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Latent is not specific heat
Specific heat (kJ/kg·K) is per degree of temperature change. Latent heat is a one-off cost at the transition, with no temperature change at all.
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Background
About latent heat
Heating ice from −10 °C to 0 °C takes 21 kJ/kg. Melting it then takes 334 kJ/kg with no rise in temperature at all, and boiling the water takes 2,257.
That hidden energy is why sweat cools you, why steam burns so badly, and why a pan of water sits at 100 °C however hard you heat it.