Moles of Gas at STP Calculator
At standard temperature and pressure (0 degrees C, 1 atm), one mole of any ideal gas occupies 22.414 liters. This molar volume is a cornerstone of gas stoichiometry and allows chemists to convert between volume and moles without needing mass or molar mass. The calculator works in both directions: enter a volume in liters to find moles, or enter moles to find volume. It also lets you convert to mass in grams if you provide the molar mass of the gas.
Moles of gas at STP formula
n = V / 22.414 L/mol (at 0 C, 1 atm)
Where n is moles and V is volume in liters. Mass = n * M where M is molar mass in g/mol. The molar volume 22.414 L/mol applies to ideal gases at 0 degrees C and 1 atm (101.325 kPa).
Key points about gas volumes at STP
- 22.414 L/mol is the classic molar volume at 0 degrees C and 1 atm (pre-1982 IUPAC definition).
- The 2013 IUPAC STP (0 degrees C, 100 kPa) gives a molar volume of 22.711 L/mol.
- All ideal gases have the same molar volume at the same temperature and pressure (Avogadro's law).
- Example: 11.207 L of nitrogen gas (N(2)) at STP contains 0.50 mol and has a mass of 14.01 g.
- At SATP (25 degrees C, 100 kPa), the molar volume is 24.465 L/mol.
Frequently asked questions
What is STP in chemistry?
STP stands for Standard Temperature and Pressure. IUPAC defines STP as 0 degrees C (273.15 K) and 100 kPa. At STP, one mole of an ideal gas occupies 22.711 L. Older texts (pre-1982 IUPAC) used 1 atm (101.325 kPa), giving a molar volume of 22.414 L/mol.
Which molar volume should I use, 22.414 or 22.711 L/mol?
This calculator uses the classic 22.414 L/mol (0 C, 1 atm), which is still the most common value used in textbooks and standardized tests. The 2013 IUPAC recommendation gives 22.711 L/mol at 0 C and 100 kPa. Check which definition your course or exam uses.
Does this formula apply to all gases?
The formula applies to ideal gases. Real gases deviate slightly from ideal behavior, especially at high pressures or low temperatures. For most practical lab calculations at STP, the ideal gas approximation is very accurate.
How do I convert liters to moles at STP?
Divide the volume in liters by 22.414 (using the classic STP). For example, 44.828 L of gas at STP is 44.828 / 22.414 = 2.00 mol.
What is the molar volume at SATP?
SATP (Standard Ambient Temperature and Pressure) is 25 degrees C and 100 kPa. The molar volume at SATP is 24.465 L/mol, which is larger than at STP because the higher temperature expands the gas.
Official sources
- IUPAC: IUPAC Gold Book - Standard conditions.
- NIST Chemistry WebBook: NIST fluid properties.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.