Gas Stoichiometry at STP Calculator
Convert between moles of a substance and the volume of gas it produces or consumes at STP using the molar volume and a balanced mole ratio.
How it works
V_gas = moles(known) × mole-ratio × molar volume · molar volume ≈ 22.414 L/mol at 0 °C, 1 atm
At standard temperature and pressure one mole of any ideal gas occupies the same molar volume — about 22.414 L at the classic 0 °C and 1 atm (22.711 L under the modern IUPAC 100 kPa definition). Gas stoichiometry uses the balanced equation’s mole ratio to convert moles of a known reactant or product into moles of gas, then multiplies by the molar volume to get a volume you can measure.
Worked example
Decomposing 2 mol of CaCO₃ releases CO₂ in a 1:1 ratio, so 2 mol of gas forms. At classic STP the volume is 2 × 22.414 = 44.83 L of CO₂.
Sources: Molar volume — Wikipedia
Frequently asked questions
Which STP definition should I use?
Older textbooks and exams use 0 °C and 1 atm (22.414 L/mol). Since 1982 IUPAC defines STP as 0 °C and 100 kPa, giving 22.711 L/mol. Pick the one your course specifies.
Does the molar volume hold for any gas?
For an ideal gas, yes — it does not depend on the identity of the gas. Real gases deviate slightly, especially at high pressure or low temperature, but the approximation is excellent at STP.
What if conditions are not STP?
Use the ideal gas law PV = nRT to find the volume at the actual temperature and pressure instead of the fixed molar volume.
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This calculator is for educational purposes. Double-check important results before acting on them.