What is the ideal gas law?

The ideal gas law is PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the universal gas constant (0.082057 L·atm·mol⁻¹·K⁻¹), and T is temperature in Kelvin.

What is molar volume at STP?

At STP (Standard Temperature and Pressure: 0 °C / 273.15 K and 1 atm), one mole of an ideal gas occupies 22.414 L.

What is molar volume at SATP?

At SATP (Standard Ambient Temperature and Pressure: 25 °C / 298.15 K and 1 bar), one mole of an ideal gas occupies 24.789 L.

When does the ideal gas law break down?

The ideal gas law is an approximation. It becomes inaccurate at very high pressures or very low temperatures, where intermolecular forces and molecular volume become significant. For those conditions, use the van der Waals equation instead.

Why must temperature be in Kelvin?

The gas constant R is defined using the Kelvin scale. Kelvin starts at absolute zero, ensuring the relationship PV = nRT is linear and physically meaningful. Negative Kelvin values are not physically possible.

Can I calculate volume for multiple moles?

Yes. Change the "Amount (moles)" field to any positive value. The molar volume (V/n) stays the same for a given T and P, but the total volume scales with n.

Molar Volume Calculator

Name: Molar Volume Calculator
Availability: InStock
Author: Nham Vu

Calculate the molar volume of an ideal gas at any temperature and pressure using the ideal gas law (V = nRT/P).

Gas Parameters

Temperature

= 273.15 K

Pressure

Amount (moles)

Molar Volume

—

L/mol

Total volume (V) —

Temperature (K) —

Pressure (atm) —

Standard Condition Reference

STP 0 °C, 1 atm

22.414 L/mol

SATP 25 °C, 1 bar

24.789 L/mol

Ideal Gas Law

PV = nRT

R (gas constant)0.082057 L·atm·mol⁻¹·K⁻¹

V/n (molar volume)= RT / P

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Summary

Calculate the molar volume of an ideal gas at any temperature and pressure using the ideal gas law (V = nRT/P).

How it works

Enter the temperature in Kelvin (or switch to Celsius — the tool converts automatically).
Enter the pressure in atm, kPa, mmHg, or bar using the unit selector.
Enter the number of moles (default is 1 mol for pure molar volume).
Click Calculate to apply the ideal gas law: V = nRT/P.
The result shows molar volume in L/mol, total volume in liters, and comparison to STP / SATP values.

Use cases

Chemistry students solving ideal gas law problems.
Lab work requiring volume estimates for gas samples.
Engineering calculations involving gas storage or reaction chambers.
Verifying that a gas behaves nearly ideally at low pressure and high temperature.
Quick reference for the molar volume at STP (22.414 L/mol) or SATP (24.789 L/mol).
Teaching demonstrations of how temperature and pressure affect gas volume.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu