# Gas Density Calculator

Reviewed by Rijk de Wet
Last updated: Aug 24, 2022

Our gas density calculator helps you to calculate the density of gas at a definite pressure and temperature.

• What density is;
• How the density of gas differs from liquid and solid;
• Whether natural gas is heavier than air; and
• Whether air is a liquid or not.

## What is density?

Density refers to how tightly packed a substance is within a particular space.

The higher the density, the more tightly packed the substance is. Solid and liquid typically have a higher density than gas.

The density of gases is affected by temperature and pressure.

Density is represented by the Greek letter $\rho$.

## How the density of gas differ from other states of matter

Unlike the density of solids or liquids, the density of gas is changeable. This is because gas is not compact, and its molecules are affected by temperature and pressure.

Because of this characteristic, gas density is calculated differently from liquids and solids. Two ways that the density of gas differs drastically from solids are:

• When the temperature of gas increases, the molecules move further apart. This causes a decrease in density.
• When we apply pressure to gas, its molecules draw closer together. This increases the density.

## How to find the density of gas with the ideal gas law

You typically need to know the mass and volume to find the density. With gas, as the volume goes up, the density goes down and vice versa.

To calculate the density of gas, we use the ideal gas law:

$\footnotesize PV = nRT$
• $P$ represents pressure.
• $V$ represents volume.
• $n$ represents the number of moles of gas.
• $R$ is the universal gas constant. It is equal to $8.314462618\ \text{J}\cdot\text{mol}^{-1}\cdot\text{K}^{-1}$.
• $T$ is the absolute temperature in Kelvin ($\text{K}$).

To calculate the volume of the gas, we need to make volume the subject of the formula. So the gas law rewritten to find the volume is:

$\footnotesize V = nRT/P$

To find the mass of the gas, you use the number of moles of the gas divided by the molecular mass ($M$). So, this means that:

$\footnotesize n = m/M$

Now that we have established that $n = m/M$, we can replace $n$ with the mass value in the equation we use for volume. So we now have:

$\footnotesize V = mRT/MP$

Since density is mass per volume, we need to divide both sides by mass to get to the formula for density. So our new equation is now:

$\footnotesize V/m = RT/MP$

To get the mass per volume, we need to invert this equation. With this, we get:

$\footnotesize \begin{split} m/V &= MP/RT \\ \therefore \rho &= MP/RT \end{split}$

🙋 You can also calculate density without knowing the molar mass. In our ideal gas density calculator we calculate the density using pressure, temperature, and a specific gas constant.

## How our gas density calculator works

Our gas density calculator employs this formula: $\rho = MP/RT$ to find the density of gas. It takes in the pressure, temperature, and molar mass of gas and calculates the density. Because $R$ is a constant, we do not require you to enter this value.

When you enter these values, the molar mass is divided by $1,\!000$ (to convert it to $\text{kg}/\text{mol}$, the actual unit for the molar mass of gas) and then multiplied by pressure. This is further divided by the universal gas constant times the temperature.

So if the given molar mass is $28\ \text{g}/\text{mol}$, the temperature is $50\ \text{K}$, and the pressure is $10\ \text{Pa}$. We will substitute these values into the density equation to calculate the density. So now we will have:

$\footnotesize \begin{split} \rho &= \frac{(28\ \text{g}/\text{mol})/ 1,\!000 \times 10\ \text{Pa}}{8.3145 \times 50\ \text{K}} \end{split}$

If you are interested in other similar calculators you should check out this list:

## FAQ

### Is natural gas heavier than air?

No, natural gas is not heavier than air.

The molar mass of natural gas ranges from 16 to 18 g/mol, while the air we breathe weighs about 29 g/mol.

### Is air a liquid?

No, air is not a liquid, it is a gas. In fact, the air we breathe is made up of several gasses. These are:

• Oxygen;
• Carbon dioxide;
• Nitrogen;
• Water vapor;
• Argon;
• Neon;
• Methane;
• Krypton;
• Xenon;
• Ozone;
• Nitrogen dioxide;
• Iodine;
• Carbon monoxide; and
• Ammonia.
Pressure (P)
Pa
Temperature (T)
K
Molecular mass (M)
g/
mol
Density (ρ)
kg/m³
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