Ideal Gas Density Calculator

What Is Ideal Gas Density?

Ideal gas density tells you how much mass a gas packs into a given volume under known pressure and temperature. Chemists, HVAC engineers, and atmospheric scientists use it to compare gases, size vessels, and estimate buoyancy. The ideal gas model treats molecules as point particles with no intermolecular forces.

Density From the Ideal Gas Law

Starting from $PV = nRT$ and substituting $n = m/M$, density follows:

$$\rho = \frac{PM}{RT}$$

Here $P$ is pressure in pascals, $M$ is molar mass in kg/mol, $R = 8.314\ \text{J mol}^{-1}\text{K}^{-1}$, and $T$ is absolute temperature in kelvin. The result is in kg/m³, which equals g/L numerically.

Example: Dry Air at Room Temperature

At 1 atm (101,325 Pa) and 298 K with molar mass 28.97 g/mol, density is about 1.19 kg/m³. Hotter air is less dense; higher pressure increases density.

Frequently Asked Questions

What value of R should I use?

Use R = 8.314 J/(mol·K) when pressure is in pascals, molar mass is in kg/mol, and temperature is in kelvin. This calculator converts g/mol to kg/mol automatically.

Why does density drop when temperature rises?

Higher temperature means faster molecules spread out for the same pressure, so the same amount of gas occupies more volume and density falls.

Is kg/m³ the same as g/L?

Yes. One kg/m³ equals one g/L because the conversion factor between kilograms and grams matches the one between cubic meters and liters.

When is the ideal gas model inaccurate?

At very high pressure or near the condensation point, real gases deviate. For many engineering estimates at moderate conditions, the ideal model is close enough.

How do I convert atm to pascals?

Multiply atmospheres by 101,325. One standard atmosphere equals 101,325 Pa exactly.

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Ideal Gas Density Calculator

What Is Ideal Gas Density?

Density From the Ideal Gas Law

Example: Dry Air at Room Temperature

Frequently Asked Questions

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