Gas Density Calculator
Calculate real gas density from pressure, temperature, molecular weight (or specific gravity), and compressibility factor using the real gas equation of state.
Gas Properties
ρ = P × MW / (Z × R × T)
R = 10.7316 psia·ft³/(lb-mol·°R). T in °R = T(°F) + 459.67.
Gas Density
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Density (kg/m³)
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Specific Gravity
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Mol. Weight
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How this was calculated
Real gas law: PV = ZnRT. Rearranging for density: ρ = PM / (ZRT), where M is molecular weight and R = 10.7316 psia·ft³/(lb-mol·°R).
Specific gravity: SG = MW_gas / MW_air, where MW_air = 28.967 lb/lb-mol.
Z-factor: The compressibility factor accounts for non-ideal gas behavior. For quick estimates, use Z = 0.85-0.90 for sweet gas at moderate pressures. For accurate Z, use the Standing-Katz chart or Hall-Yarborough correlation.
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Book a free strategy call →Understanding Gas Density Calculations
Gas density is a critical parameter in petroleum engineering, affecting flow calculations, pressure gradients, separator design, and pipeline hydraulics. Unlike liquids, gas density varies significantly with pressure, temperature, and composition. The real gas equation of state accounts for molecular interactions through the compressibility factor Z, which deviates from unity at high pressures and low temperatures typical of reservoir and wellbore conditions.
For natural gas mixtures, the apparent molecular weight can be calculated from composition or estimated from the gas specific gravity (relative to air at standard conditions). This calculator supports both inputs. All calculations run entirely in your browser with no data sent to any server. Built by Groundwork Analytics.