Gas Density Calculator
Calculate the density of a gas at line conditions from its molecular weight, pressure, temperature and compressibility factor.
- ρ = P × M ÷ (Z × R × T) = 500,000 × 28.965 ÷ (1 × 8314.46 × 298.15) = 5.8422 kg/m³
Gas Density Formula
P is absolute pressure (Pa), M molecular weight (kg/kmol), Z the compressibility factor, R = 8314.46 J/(kmol·K) and T the absolute temperature (K).
Worked example
Air at 5 bar(a) and 25 °C: ρ = 500,000 × 28.965 ÷ (8314.46 × 298.15) = 5.84 kg/m³.
Frequently Asked Questions
What is the density of air?
About 1.293 kg/m³ at 0 °C and 1.204 kg/m³ at 20 °C, both at 1.01325 bar.
What is compressibility factor Z?
A correction for real gas behaviour. Z = 1 for an ideal gas; natural gas at 50 bar is around 0.9.
Can I use this for steam?
Only as a rough estimate for superheated steam far from saturation. Use steam tables for accurate values.
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