Ideal Gas Volume Calculator

Created by Steven Wooding
Reviewed by Adena Benn
Last updated: Aug 11, 2022

This ideal gas volume calculator finds the volume of an ideal gas given the amount of gas and its temperature. We'll explain in this short article:

  • What an ideal gas is;
  • How to calculate its volume using the ideal gas law; and
  • How to calculate the molar volume of an ideal gas at STP (standard temperature and pressure).

What is an ideal gas?

An ideal gas is one that consists of molecules that are modeled as point-like particles that have no interactions. Such a theoretical gas obeys the gas laws precisely, making the math much easier.

The good news is that certain gases at normal temperatures and pressures behave like an ideal gas without much error. These include hydrogen, oxygen, nitrogen, noble gases, carbon dioxide, and air. The difference between these real gases and an ideal gas is smaller at higher temperatures and lower pressures.

How to calculate volume using the ideal gas law

The ideal gas law is expressed in math by the following formula:

PV=nRT\small PV = nRT


  • PP – Pressure;
  • VV – Volume;
  • nn – Number of gas particles in moles;
  • TT – Temperature; and
  • RR – Gas constant, which is equal to 8.3145 J·K-1·mol-1.

To find the volume of an ideal gas, we can divide both sides of the above equation by PP to get:

V=nRTP\small V = \frac{nRT}{P}

Using our ideal gas volume calculator is pretty straightforward:

  1. Enter the pressure of the gas (select your preferred units first).

  2. Input the temperature of the gas.

  3. Finally, enter the number of moles of the gas.

  4. The calculator will then instantly display the resulting volume of the ideal gas.

If you only know the mass of the gas, you can use the advanced mode of the calculator to find the number of moles using the mass and the molar mass of the gas.

How to calculate the molar volume of an ideal gas at STP

You can use the ideal gas volume calculator to find the molar volume of an ideal gas at standard temperature and pressure (STP) – or any other temperature or pressure.

All you need to do is set the amount of substance variable to 1 mole. Let's substitute the values for standard temperature and pressure (273.15 K and 100,000 Pa, respectively) into the ideal gas volume equation:

V=nRTP=1×8.3145×273.15100000=0.02271095 m322.71095 liters\small \begin{align*} V &= \frac{nRT}{P}\\[1em] &= \frac{1 \times 8.3145 \times 273.15 }{100000}\\[1em] &= 0.02271095\ \text{m}^3\\[.5em] &\equiv 22.71095\ \text{liters} \end{align*}

Other ideal gas calculators

Here are some other calculators that calculate the parameters of an idea gas:


What volume will 2.0 moles of nitrogen occupy?

45.4 liters. Here's how to calculate this answer:

  1. Assume that the temperature and pressure of the gas are 273.15 K and 100,000 Pa, respectively.
  2. Multiply the number of moles, 2, by the gas constant (8.3145) and the temperature.
  3. Divide by the pressure. The result will be in cubic meters.
  4. To convert the result to liters, multiply by 1000.

When does a real gas behave like an ideal gas?

A gas acts more like an ideal gas at higher temperatures and lower pressures. This is because the potential energy between the gas molecules becomes negligible compared with their kinetic energy. Furthermore, the size of the molecules becomes less significant than the empty space between them at lower pressures.

Steven Wooding
Pressure (p)
Temperature (T)
Amount of substance (n)
Volume (V)
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