Air Density Calculator
Air density from temperature, pressure or altitude and humidity.
About this tool
Enter the air temperature and humidity, then either the pressure in hPa or an altitude to use the standard atmosphere. The result shows density in kg/m³ and lb/ft³, how it compares with standard sea-level air, and the density altitude.
What changes air density
Standard sea-level air at 15°C and 1013.25 hPa has a density of 1.225 kg/m³. Warmer air is less dense, lower pressure (higher altitude or a low-pressure system) is less dense, and moist air is slightly less dense than dry air because water vapour molecules (18 g/mol) are lighter than the nitrogen and oxygen they replace (about 29 g/mol). The calculator splits the air into dry air and water vapour and adds their densities, ρ = pd/(RdT) + pv/(RvT), with the Magnus formula for saturation vapour pressure. Density altitude is the height in the standard atmosphere that has the same density: on a hot 30°C day at a 1,500 m airfield, it is about 2,350 m, which reduces engine power, lift and propeller thrust. Air density also matters for cycling and running aerodynamics, wind turbine output and ballistics. Honest limits: this is an ideal-gas model, accurate to well under 1% in normal weather; for aircraft performance always use the official charts. The ideal gas law calculator and the density calculator are related.
Frequently asked questions
What is the density of air?
About 1.225 kg/m³ at sea level and 15°C, falling to about 1.16 kg/m³ at 30°C.
Does humidity make air lighter or heavier?
Lighter. Water vapour is less dense than dry air, so humid air at the same temperature and pressure is slightly less dense.
What is density altitude?
The altitude in the standard atmosphere with the same air density as current conditions. Pilots use it to judge take-off and climb performance.
Should I use station pressure or sea-level pressure?
Station pressure (the actual pressure where you are). Sea-level-adjusted pressure from forecasts will overestimate density at altitude.
Is my data sent anywhere?
No. Everything is calculated in your browser, and nothing is stored or sent.