How this calculator works
Use the ideal gas law for a fixed amount of gas. IUPAC standard conditions use 273.15 K and 100 kPa; an older common convention uses one atmosphere, or 101.325 kPa. Choose the convention explicitly because the resulting molar volumes differ. Pressures must be absolute and temperatures must be kelvins internally. Real-gas compressibility, water vapour correction and gas dissolution are excluded.
Formula
P V/T = Pstandard Vstandard/Tstandard; n = P V/(R T). At IUPAC STP, molar volume is about 22.71095 L/mol.
Worked example
1 L at 273.15 K and 100 kPa is 1 L at IUPAC STP. A 2 L sample at 546.30 K and the same pressure becomes 1 L at IUPAC STP.
Advertisement
Frequently asked questions
Is STP always one atmosphere?
No. IUPAC uses 100 kPa. One atmosphere is a separate traditional convention provided here.
Can a negative Celsius temperature be valid?
Yes, provided its absolute kelvin temperature remains positive.
Will this correct for humid gas?
No. Use the dry gas partial pressure when water vapour is present.