Calculate natural gas density at operating pressure and temperature using the real gas equation and a Z factor you supply.
Typical: 0.55-0.70 (sweet gas), 0.70-0.90 (rich gas)
Typical range: 0.70-1.00. Enter Z from the Z-Factor calculator, a Standing-Katz chart, or AGA-8 (computed separately).
Real gas: Use for P > 100 psig, with a Z-factor you supply
Ideal gas: Only for preliminary estimates at low pressure
Understand ideal gas law, real gas behavior, Z-factor correlations, and equation of state methods
Density of common gases at standard conditions (60°F, 14.696 psia), from ρ = MW·P/(R·T) with Z ≈ 1. Use the calculator above for density at any operating pressure and temperature with the real-gas Z-factor.
| Gas | Molar mass (lb/lbmol) | Density (lb/ft³) |
|---|---|---|
| Hydrogen (H₂) | 2.016 | 0.0053 |
| Methane (CH₄) | 16.043 | 0.0423 |
| Nitrogen (N₂) | 28.013 | 0.0738 |
| Air | 28.964 | 0.0763 |
| Ethane (C₂H₆) | 30.070 | 0.0792 |
| Carbon dioxide (CO₂) | 44.010 | 0.1160 |
Natural gas density is calculated using the Real Gas Equation of State: ρ = (P × MW) / (Z × R × T), where P is absolute pressure, MW is molecular weight, Z is the compressibility factor, R is the gas constant, and T is absolute temperature.
The Z-factor (compressibility factor) is a correction term that accounts for the deviation of a real gas from ideal gas behavior. At high pressures, natural gas becomes denser than an ideal gas would predict, making Z less than 1.0.
Gas density is used to determine mass flow rates, calculate pipeline inventory (line pack), and size compressors and equipment. Custody transfer requires a compressibility factor calculated from gas composition (AGA Report No. 8 or ISO 12213), which this calculator does not perform.
At standard conditions (60°F, 14.696 psia), methane — the main component of natural gas — has a density of about 0.0423 lb/ft³, compared with 0.0763 lb/ft³ for air. Density rises with pressure and falls with temperature, corrected by the compressibility factor Z.