Air Density Calculator
Compute moist air density in kg/m³
How to Use This Calculator
Enter Temperature
Provide air temperature in degrees Celsius.
Enter Pressure
Provide station pressure in hPa (default 1013.25).
Enter Relative Humidity
Provide RH as a percentage (0–100%).
Press Calculate
View moist air density and related pressures.
Formula
e_s(T) = 6.112 · exp((17.67·T)/(T+243.5)) [hPa]
e = RH/100 · e_s(T), p_d = p − e
ρ = p_d·100/(R_d·T_K) + e·100/(R_v·T_K)
Constants: R_d = 287.058 J/(kg·K), R_v = 461.495 J/(kg·K)
Example: T=20°C, p=1013.25 hPa, RH=50% → ρ ≈ 1.204 kg/m³
About Air Density
Air density affects aircraft performance, ballistics, HVAC sizing, and athletic performance. It depends on pressure, temperature, and humidity.
- Colder, higher-pressure, and drier air is denser
- Warmer and more humid air is less dense
Frequently Asked Questions
How much does humidity change density?
Effect is modest (a few percent) but noticeable for performance calculations.
Is station pressure the same as sea-level pressure?
No. Use local station pressure if available; sea-level pressure overestimates density at elevation.