# Charles’s Law Calculator

URL: https://speedycalculator.com/calculators/physics/charles-law/
Last updated: 2026-10-30

> The Charles's law calculator finds the final volume or temperature of a gas heated or cooled at constant pressure.

## Inputs

- Find
- Initial volume V₁ (L, m³, mL, ft³)
- Initial temperature T₁ (K, °C, °F)
- Final temperature T₂ (K, °C, °F)
- Final volume V₂ (L, m³, mL, ft³)

## Results

- Final volume V₂
- Final temperature T₂

## Formula

```
V₁/T₁ = V₂/T₂  (absolute temperatures)
```

## Explanation

Gases expand when heated: at constant pressure, volume is proportional to absolute temperature. Hot-air balloons rise because the heated air expands and becomes less dense.

### How to use the Charles's Law Calculator

- **Find**
- **Initial volume V₁**
- **Initial temperature T₁**
- **Final temperature T₂**
- **Final volume V₂**

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

### How it works

Choose what to find and enter the known values.

### 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 enterFindChoose one: Final volume V₂, Final temperature T₂Initial volume V₁Units: L, m³, mL, ft³Initial temperature T₁Units: K, °C, °FFinal temperature T₂Units: K, °C, °FFinal volume V₂Units: L, m³, mL, ft³

### What each result means

- **Final volume V₂** = [Initial volume V₁]×[Final temperature T₂]÷[Initial temperature T₁]
- **Final temperature T₂** = [Initial temperature T₁]×[Final volume V₂]÷[Initial volume V₁]

### Example values

How the main result changes when **Initial volume V₁** changes and everything else stays at the example values above:

Initial volume V₁ (L)Final volume V₂ (L)0.50.63640.750.954711.27291.251.59111.51.909322.5458

## Worked example

Inputs — Find: Final volume V₂; Initial volume V₁: 1 L; Initial temperature T₁: 293.15 K; Final temperature T₂: 373.15 K.

Results — **Final volume V₂ = 1.2729 L**.

## Key terms

- **Isobaric**: At constant pressure.

## FAQ

**Why must temperatures be absolute?**
Volume is proportional to kelvin temperature, not Celsius.

**What happens at absolute zero?**
An ideal gas would have zero volume – real gases liquefy first.

**How much does air expand from 20 °C to 100 °C?**
About 27%.

**Who discovered it?**
Jacques Charles (~1787), published by Gay-Lussac in 1802.

**What formula does the Charles's Law Calculator use?**
V₁/T₁ = V₂/T₂  (absolute temperatures).


## Sources

- [OpenStax – Chemistry 2e](https://openstax.org/details/books/chemistry-2e)
- [OpenStax – University Physics Volume 2](https://openstax.org/details/books/university-physics-volume-2)
- [HyperPhysics (Georgia State University)](http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html)