Input Parameters

Gas Type

Molecular Weight (g/mol)

Density at STP (kg/m³)

Input Value

From Unit

To Unit

Conditions

Standard Condition

Real Gas Correction

Standard Conditions Definitions

Standard	Temperature	Pressure	Molar Volume	Common Usage
STP	0°C (273.15 K)	1 atm (101.325 kPa)	22.414 L/mol	Chemistry, IUPAC
NTP	20°C (293.15 K)	1 atm (101.325 kPa)	24.055 L/mol	Engineering, Industry
SATP	25°C (298.15 K)	1 bar (100 kPa)	24.789 L/mol	Thermodynamics

Standard Volume Conversions

Input Value

From Standard

To Standard

Real Gas Behavior

Real gases deviate from ideal gas behavior, especially at high pressures and low temperatures. This deviation can be accounted for using compressibility factors (Z) or equations of state.

Compressibility Factor (Z)

The compressibility factor is defined as Z = PV/RT, where:

P = pressure
V = volume
R = gas constant
T = temperature

For an ideal gas, Z = 1. Real gases deviate from this value.

Equations of State

Common equations used to model real gas behavior:

Van der Waals equation
Redlich-Kwong equation
Soave-Redlich-Kwong equation
Peng-Robinson equation

Compressibility Factor Calculator

Gas Type

Critical Temperature (K)

Critical Pressure (atm)

Acentric Factor

Temperature (K)

Pressure (atm)

Common Gas Properties

Gas	Formula	Molecular Weight (g/mol)	Density at STP (kg/m³)	Critical Temp (K)	Critical Press (atm)	Acentric Factor
Air	-	28.97	1.225	132.5	37.2	0.022
Nitrogen	N₂	28.01	1.2506	126.2	33.9	0.037
Oxygen	O₂	32.00	1.429	154.6	50.4	0.022
Hydrogen	H₂	2.016	0.0899	33.2	12.8	-0.216
Carbon Dioxide	CO₂	44.01	1.977	304.2	72.9	0.225
Methane	CH₄	16.04	0.717	190.6	45.4	0.008
Helium	He	4.003	0.1785	5.19	2.27	-0.390
Argon	Ar	39.95	1.784	150.9	48.1	-0.002

Gas Conversion Calculator