# Ideal Gas Density Calculator

URL: https://speedycalculator.com/calculators/physics/ideal-gas-density/
Last updated: 2026-10-30

> The ideal gas density calculator finds the density of a gas from its molar mass (or specific gas constant), pressure and temperature, with values for common gases.

## Inputs

- Gas
- Molar mass M (g/mol)
- Pressure p (kPa, Pa, bar, atm, psi, MPa)
- Temperature T (K, °C, °F)

## Results

- Molar mass
- Specific gas constant
- Density ρ

## Formula

```
ρ = p·M / (R·T) = p / (R_s·T)
```

## Explanation

Gas density changes with pressure and temperature. Helium is so much less dense than air that it lifts balloons; carbon dioxide is denser and pools in low places.

### How to use the Ideal Gas Density Calculator

- **Gas**
- **Molar mass M (g/mol)**
- **Pressure p**
- **Temperature T**

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

### How it works

Choose the gas, enter the pressure and temperature.

### 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 enterGasChoose one: Air, Nitrogen N₂, Oxygen O₂, Hydrogen H₂ …Molar mass M (g/mol)A numberPressure pUnits: kPa, Pa, bar, atm, psi, MPaTemperature TUnits: K, °C, °F

### What each result means

- **Specific gas constant** = 8.314462618÷([Molar mass]÷1000)
- **Density ρ** = [Pressure p]×[Molar mass]÷1000÷(8.314462618×[Temperature T])

### Example values

How the main result changes when **Molar mass M** changes and everything else stays at the example values above:

Molar mass M (g/mol)Density ρ (kg/m³)14.481.22521.721.22528.971.22536.211.22543.451.22557.931.225

## Worked example

Inputs — Gas: Air; Pressure p: 101.325 kPa; Temperature T: 288.15 K.

Results — Molar mass = 28.965 g/mol; Specific gas constant = 287.05205 J/(kg·K); **Density ρ = 1.225 kg/m³**.

## Key terms

- **Specific gas constant**: R divided by molar mass.

## FAQ

**What is the density of air at sea level?**
About 1.225 kg/m³ at 15 °C.

**Why is helium so light?**
Its molar mass is only 4 g/mol.

**Is the ideal gas model accurate?**
Within about 1% near atmospheric conditions.

**How does pressure affect density?**
Density is proportional to absolute pressure.

**What formula does the Ideal Gas Density Calculator use?**
ρ = p·M / (R·T) = p / (R_s·T).


## Sources

- [NIST – Fundamental physical constants](https://physics.nist.gov/cuu/Constants/)
- [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)