MAXScanner physics & engineering calculator
Air Density Calculator — Temperature, Pressure & Humidity
Calculate moist-air density from temperature, barometric pressure and relative humidity using dry-air and water-vapor partial pressures.
Last updated: September 17, 2026
Results
Enter valid temperature, positive absolute pressure and RH 0–100%
Formula, example and assumptions
ρ=pd/(RdT)+pv/(RvT), where pv=RH·psat and pd=p−pv.
At about 20°C and 101.325 kPa, dry air density is close to 1.20 kg/m³; humidity lowers density slightly at the same pressure and temperature.
- Pressure is absolute barometric pressure, not gauge pressure.
- Saturation vapor pressure is approximated with a Magnus-type relation for ordinary atmospheric conditions.
Frequently asked questions
Does humid air weigh more?
At the same temperature and total pressure, humid air is less dense because water-vapor molecules replace heavier average dry-air molecules.
Why does temperature reduce air density?
At fixed pressure, warmer gas occupies more volume, so mass per unit volume falls.