# Latent Heat Calculator

URL: https://speedycalculator.com/calculators/physics/latent-heat/
Last updated: 2026-10-30

> The latent heat calculator finds the energy needed to melt or boil (or released when freezing or condensing) a mass of a substance, with fusion and vaporisation values for common materials.

## Inputs

- Mass m (kg, g, mg, t, lb, oz)
- Substance
- Phase change
- Latent heat L (kJ/kg, J/kg, J/g)

## Results

- Latent heat used
- Energy Q

## Formula

```
Q = m·L
```

## Explanation

During a phase change, heat goes into breaking bonds rather than raising temperature. Melting ice absorbs 334 kJ per kilogram – which is why ice cools drinks so well – and boiling water absorbs nearly seven times more.

### How to use the Latent Heat Calculator

- **Mass m**
- **Substance**
- **Phase change**
- **Latent heat L**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Choose the substance and the phase change, and enter the mass.

### Tips

- Use absolute temperature (K) in gas laws and efficiency formulas.
- Temperature differences are the same in K and °C.
- Heat = mass × specific heat × temperature change when no phase change occurs.
- Phase changes need latent heat at a constant temperature.

### Common mistakes to avoid

- Using °C in pV = nRT.
- Forgetting latent heat during melting or boiling.
- Confusing heat capacity (J/K) with specific heat (J/(kg·K)).

### Inputs explained

FieldWhat to enterMass mUnits: kg, g, mg, t, lb, ozSubstanceChoose one: Water / ice, Ethanol, Ammonia, Mercury …Phase changeChoose one: Melting / freezing (fusion), Boiling / condensing (vaporisation)Latent heat LUnits: kJ/kg, J/kg, J/g

### Example values

How the main result changes when **Mass m** changes and everything else stays at the example values above:

Mass m (kg)Energy Q (J)0.5167,0000.75250,5001334,0001.25417,5001.5501,0002668,000

## Worked example

Inputs — Mass m: 1 kg; Substance: Water / ice; Phase change: Melting / freezing (fusion).

Results — Latent heat used = 334,000 J/kg; **Energy Q = 334,000 J**.

## Key terms

- **Latent heat**: Energy for a phase change at constant temperature.

## FAQ

**Why doesn't temperature change during melting?**
Energy goes into breaking bonds between molecules.

**Why is the latent heat of vaporisation larger?**
Molecules must be fully separated.

**Why do steam burns hurt so much?**
Condensing steam releases 2,257 kJ/kg on your skin.

**What is the latent heat of ice?**
334 kJ/kg.

**What formula does the Latent Heat Calculator use?**
Q = m·L.


## Sources

- [OpenStax – University Physics Volume 2](https://openstax.org/details/books/university-physics-volume-2)
- [The Engineering ToolBox](https://www.engineeringtoolbox.com/)
- [NIST – Fundamental physical constants](https://physics.nist.gov/cuu/Constants/)