Air Density Calculator
Calculate the density of air at any temperature, pressure, and humidity.
Essential for aerodynamics, aviation, and physics calculations.
Air density is the mass of air per unit volume, typically expressed in kilograms per cubic meter (kg/m³). It varies with temperature, pressure, and humidity, and affects everything from aircraft lift to sports ball trajectories to the efficiency of wind turbines.
The Ideal Gas Law for Air
Dry air density can be calculated using the ideal gas law:
ρ = P / (R_specific × T)
Where:
- ρ = air density (kg/m³)
- P = absolute pressure (Pa)
- R_specific = specific gas constant for dry air = 287.058 J/(kg·K)
- T = absolute temperature (Kelvin) = °C + 273.15
For example, at sea level (101,325 Pa) and 20°C (293.15 K): ρ = 101,325 / (287.058 × 293.15) = 1.204 kg/m³
Effect of Humidity
Humid air is actually less dense than dry air at the same temperature and pressure. This is because water vapor (molecular weight 18 g/mol) is lighter than the average mixture of nitrogen (28) and oxygen (32) it displaces. The effect is small but significant for precision calculations.
The density of moist air: ρ_moist = ρ_dry × (1 − 0.378 × P_v / P)
Where P_v is the partial pressure of water vapor, calculated from relative humidity and saturation pressure.
Air Density Reference Values
| Condition | Temperature | Pressure | Density (kg/m³) |
|---|---|---|---|
| Sea level, dry (ISA standard) | 15 °C | 1013 hPa | 1.225 |
| Sea level, dry | 20 °C | 1013 hPa | 1.204 |
| Sea level, dry | 30 °C | 1013 hPa | 1.165 |
| 1,000 m, ISA | 8.5 °C | 899 hPa | 1.112 |
| 2,000 m, ISA | 2.0 °C | 795 hPa | 1.007 |
| 3,000 m, ISA | −4.5 °C | 701 hPa | 0.909 |
The three altitude rows are standard-atmosphere figures, so they carry the ISA temperature for that height, not 15 °C. That matters if you are checking them against the calculator: enter 2,000 m worth of pressure with 15 °C rather than the standard 2.0 °C and you get about 0.961, not 1.007. Neither number is wrong, they are answering different questions. Temperature moves density about as much as altitude does over the range people actually fly and race in.
Applications
- Aviation: Aircraft lift depends on air density; pilots must account for density altitude, especially when departing from high-altitude airports on hot days.
- Sports: Baseball, cricket, and golf balls fly farther in lower density air (high altitude, hot days).
- Wind turbines: Power output is proportional to air density, so turbines produce less power at high altitudes.
- HVAC: Airflow calculations for duct sizing depend on air density.
Wind turbine power impact
Wind power scales linearly with air density:
P = 0.5 × ρ × A × v³ × Cp
Where A is rotor swept area (m²), v is wind speed (m/s), and Cp is the turbine power coefficient.
A turbine at Denver (1,609 m altitude, P ≈ 83,600 Pa, T = 15°C) sees ρ = 83,600 / (287.058 × 288.15) = 1.011 kg/m³, about 17% less than the 1.225 sea-level standard. At the same wind speed, that turbine produces 17% less power than an identical machine on the coast. This is why developers run density corrections on every site before signing a power purchase agreement.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.