# Molar volume

This calculator calculates the molar volume of an ideal gas at different conditions (temperature and pressure)

This online calculator calculates the molar volume of an ideal gas at different conditions (different temperature and pressure). You can read about the formula and the most commonly used conditions below the calculator.

The calculation uses the ideal gas equation:

The ideal gas equation is a good approximation for many common gases. And, for a given temperature and pressure, the molar volume is the same for all ideal gases, and is known to the same precision as the gas constant: R = 0.082 057 338(47) L atm K−1 mol−1, that is a relative standard uncertainty of 5.7×10−7, according to the 2014 CODATA recommended value.^{1}

Since it is the same for all gases, it can be pre-calculated for most commonly used conditions. That is, for STP – standard temperature and pressure (273.15 K, 101.325 kPa) – the molar volume of an ideal gas is 22.413962x10-3 m3 mol-1 with standard uncertainty 0.000013 x 10-3 m3 mol-1.^{2}

For convenience, I've listed the molar volume for several other commonly used conditions in the table below.

Condition | AKA | Temperature | Pressure | Molar volume, liters |
---|---|---|---|---|

Standard Temperature and Pressure (NIST) | STP | 0C (273.15K) | 101.325kPa (1atm) | 22.414 |

Standard Temperature and Pressure (IUPAC) | STP | 0C (273.15K) | 100.000kPa (1bar) | 22.711 |

Normal Temperature and Pressure | NTP | 20C (293.15K) | 101.325kPa (1atm) | 24.055 |

Standard Ambient Temperature and Pressure | SATP | 25C (298.15K) | 101.325kPa (1atm) | 24.465 |

There are also terms such as RTP – room temperature and pressure, and SLC – standard laboratory conditions, However, there is no single definition for them, and different organizations can use different definitions. Using this calculator, you can calculate the molar volume of a gas for arbitrary temperature and pressure. Just note that for big values (hundreds of atmospheres and thousands of degrees) real gases divert from ideal gas law (that's why they are not "ideal") and this formula can't be used.

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