Science & Engineering

STP Molar Volume (Ideal Gas at Standard Conditions)

Pick a standard like classic STP or IUPAC SATP and you get the molar volume and ideal-gas quantities. You can also enter your own temperature and pressure.

How to use
  1. Choose a standard: STP, SATP, IUPAC STP, or NTP.
  2. Or enter custom temperature and pressure values.
  3. Enter moles or volume to convert between them.
For study and estimation. Verify against authoritative data before relying on a result.
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Worked examples

StandardConditionsMolar volume (L/mol)
Classic STP0°C, 1 atm22.414
IUPAC STP (1982+)0°C, 1 bar22.711
IUPAC SATP25°C, 1 bar24.789
NTP20°C, 1 atm24.055

Common questions

Is the molar volume always 22.4 L?

Only for classic STP at 0°C and 1 atm. The IUPAC 1 bar standard gives 22.71 L, and warmer standards give larger volumes.

Why are there several STP definitions?

Different bodies set different reference conditions over time, mainly switching from 1 atm to 1 bar pressure, which slightly changes the molar volume.

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