Standard Temperature and Pressure (STP) Calculator
Enter the number of moles of an ideal gas and choose the conditions standard (old IUPAC STP at 1 atm, new IUPAC STP at 1 bar, or SATP at 25 °C) to get the volume, molar volume, and full thermodynamic conditions.
Conditions standard
mol
Volume of the ideal gas using PV = nRT
- 1
Numerator: n × R × T
1 × 8.314 × 273.15 = 2,270.969R = 8.314 J mol⁻¹ K⁻¹ - 2
Volume: nRT ÷ P
2,270.969 ÷ 100,000 = 0.02271 - 3
Convert to litres (× 1000)
0.02271 × 1000 = 22.710
How does this calculator work?
At IUPAC STP (0 °C, 100 kPa), one mole of ideal gas occupies 22.711 L (old STP at 1 atm: 22.414 L; SATP at 25 °C: 24.789 L). Volume = nRT/P with R = 8.314 J mol⁻¹ K⁻¹. Enter moles and choose the conditions standard to get the exact volume and particle count.
Formula
How this is calculated
Standard Temperature and Pressure (STP) is a reference point defined by IUPAC for reporting gas-phase data. The original definition (widely used before 1982) set T = 0 °C (273.15 K) and P = 1 atm (101 325 Pa), giving a molar volume of 22.414 L/mol for an ideal gas. In 1982 IUPAC changed the pressure reference to exactly 100 000 Pa (1 bar), shifting the molar volume to 22.711 L/mol. Many chemistry textbooks and problems still use the old 22.4 L/mol value, so this calculator lets you choose between both STP definitions and also SATP (Standard Ambient Temperature and Pressure: 25 °C, 100 kPa), which gives a molar volume of 24.789 L/mol and is used in thermodynamic tables.
The volume of n moles of ideal gas at any of these conditions is calculated from the ideal gas law PV = nRT, where R = 8.314 J mol⁻¹ K⁻¹. Rearranging gives V = nRT/P. This assumes ideal-gas behaviour — no intermolecular forces and negligible molecular volume. Real gases deviate from the ideal law at high pressures or very low temperatures, but at STP and SATP the deviation is small for most common gases (less than 0.1% for N₂, O₂ and Ar).
The particle count is the number of molecules: n × Nₐ, where Nₐ = 6.022 × 10²³ mol⁻¹ is Avogadro's constant.
Frequently asked questions
Under the 1982 IUPAC STP (0 °C, 100 kPa), one mole of ideal gas occupies 22.711 L. Under the older STP (0 °C, 1 atm), it occupies 22.414 L. Many textbooks still cite the old 22.4 L/mol — check which standard your course uses.
STP is 0 °C (273.15 K) and 100 kPa. SATP (Standard Ambient Temperature and Pressure) is 25 °C (298.15 K) and 100 kPa — closer to typical lab conditions. The higher temperature means each mole occupies a larger volume: 24.789 L at SATP versus 22.711 L at STP.
The calculator uses the ideal gas law, which is a good approximation at STP and SATP for most gases. For precise work with real gases (especially at high pressures or low temperatures), corrections such as the van der Waals equation are needed.
Also known as
TG we-Calculate Editorial Team. (2026). Standard Temperature and Pressure (STP) Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/standard-temperature-and-pressure-calculator
TG we-Calculate Editorial Team. "Standard Temperature and Pressure (STP) Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/standard-temperature-and-pressure-calculator.
TG we-Calculate Editorial Team, "Standard Temperature and Pressure (STP) Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/standard-temperature-and-pressure-calculator
@misc{wecalculate_standard_temperature_and_pressure_calculator, title = {Standard Temperature and Pressure (STP) Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/standard-temperature-and-pressure-calculator}}, year = {2026}, note = {TG we-Calculate} }
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