Real Gas Density Calculator
Enter gas properties, pressure, temperature, and z-factor. The calculator returns real gas density.
Calculation context and source notes
Real gas density estimates gas density at pressure and temperature using gas molecular weight or gravity and the real-gas z-factor.
Use it for gas PVT checks, pressure-gradient estimates, and gas-property calculations where nonideal gas behavior matters.
Solves for
rho_g (lb/ft³)
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Formula, variables, and sourceRelated source-backed guides
Formula, variables, and default calculation
Reproducible default result
With the default values shown below, the calculation returns rho_g = 10.32018 lb/ft³. Defaults demonstrate the implementation; they are not recommended field values.
3000
18.82855
0.85
10.732
600
Input definitions
P
psiaPressure
M_g
lb/lbmolGas Molecular Weight
z
dimensionlessGas Compressibility Factor
R
psia ft³/(lbmol °R)Gas Constant
T
°RTemperature
Output definitions
rho_g
Real Gas Density
P
Pressure
M_g
Gas Molecular Weight
Engineering use, assumptions, and limits
Use it for gas PVT checks, pressure-gradient estimates, and gas-property calculations where nonideal gas behavior matters.
Assumptions
- The gas z-factor is representative at the stated pressure and temperature.
- Pressure and temperature are absolute where required by the equation.
- Gas composition or gas gravity is known.
Limitations
- Does not model compositional phase behavior or liquid dropout.
- Accuracy depends on the z-factor and gas-property inputs.
Common mistakes
- Using gauge pressure instead of absolute pressure.
- Using Fahrenheit where Rankine is required.
- Applying a dry-gas calculation to wet gas without checking assumptions.
Source and record status
Source metadata identifies the relationship implemented by the calculator. Check the cited edition, unit basis, and scope against the engineering case before operational use.
Penn State PNG 301. Natural Gas Properties, Equation 3.71.
Open source reference