STP Gas Volume Calculator

One of the most useful shortcuts in chemistry is that a mole of any gas takes up the same volume under the same conditions, and this calculator uses that fact to convert freely between an amount of gas in moles and the volume it occupies. Choose the conditions, enter a number of moles to get the volume, or enter a volume to get the moles, and the answer updates as you type. The link between the two is the molar volume, the space one mole of gas fills. At standard temperature and pressure, zero degrees Celsius and one atmosphere, that volume is about 22.4 litres per mole, the classic figure quoted in most courses, while at room temperature and pressure, around twenty-five degrees, the commonly taught value is 24.0 litres per mole, and the calculator lets you pick whichever your syllabus uses. The reason this works for any gas comes from Avogadro's law: equal numbers of particles of any gas, behaving ideally, occupy equal volumes at the same temperature and pressure, regardless of whether the particles are light hydrogen molecules or heavy carbon dioxide. That single idea removes the need to know the identity of the gas, turning a potentially fiddly calculation into a simple multiplication or division. It is the everyday tool for working out how much gas a reaction will produce or consume, a constant feature of stoichiometry problems where you convert from moles given by an equation to a measurable volume of gas. That makes this calculator genuinely useful for chemistry students learning the mole concept, molar volume and gas stoichiometry and checking homework, and for anyone needing a quick moles-to-volume conversion for a gas. The values and a worked example are explained clearly below.

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Moles to volume

Volume to moles