# Gay-Lussac’s Law Calculator

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

> The Gay-Lussac's law calculator finds the final pressure or temperature of a gas in a rigid container heated or cooled at constant volume.

## Inputs

- Find
- Initial pressure p₁ (kPa, Pa, bar, atm, psi, MPa)
- Initial temperature T₁ (K, °C, °F)
- Final temperature T₂ (K, °C, °F)
- Final pressure p₂ (kPa, Pa, bar, atm, psi, MPa)

## Results

- Final pressure p₂
- Final temperature T₂

## Formula

```
p₁/T₁ = p₂/T₂  (absolute temperatures)
```

## Explanation

In a sealed rigid container, pressure rises in proportion to absolute temperature. That is why aerosol cans warn against heating and why tyre pressure rises after a long drive.

### How to use the Gay-Lussac's Law Calculator

- **Find**
- **Initial pressure p₁**
- **Initial temperature T₁**
- **Final temperature T₂**
- **Final pressure p₂**

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 pressure p₂, Final temperature T₂Initial pressure p₁Units: kPa, Pa, bar, atm, psi, MPaInitial temperature T₁Units: K, °C, °FFinal temperature T₂Units: K, °C, °FFinal pressure p₂Units: kPa, Pa, bar, atm, psi, MPa

### What each result means

- **Final pressure p₂** = [Initial pressure p₁]×[Final temperature T₂]÷[Initial temperature T₁]
- **Final temperature T₂** = [Initial temperature T₁]×[Final pressure p₂]÷[Initial pressure p₁]

### Example values

How the main result changes when **Initial pressure p₁** changes and everything else stays at the example values above:

Initial pressure p₁ (kPa)Final pressure p₂ (kPa)110121.257165181.8856220242.5141275303.1426330363.7711440485.0281

## Worked example

Inputs — Find: Final pressure p₂; Initial pressure p₁: 220 kPa; Initial temperature T₁: 293.15 K; Final temperature T₂: 323.15 K.

Results — **Final pressure p₂ = 242.51407 kPa**.

## Key terms

- **Isochoric**: At constant volume.

## FAQ

**Why do tyre pressures rise when driving?**
The air inside warms up at nearly constant volume.

**Should I use gauge or absolute pressure?**
Absolute pressure.

**Why do aerosol cans explode when heated?**
Pressure rises with temperature in the sealed can.

**Who discovered this law?**
Joseph Louis Gay-Lussac, around 1802.

**What formula does the Gay-Lussac's Law Calculator use?**
p₁/T₁ = p₂/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)