Ideal dry air
ρ = p / (R x T)
R = 287.05 J/(kg x K)
p = absolute pressure in Pa
Air property calculator
Air Density Calculator
Calculate dry or humid air density from temperature, pressure, and relative humidity, with a live reference table and graph for nearby temperatures.
Instant air density solver
Enter air conditions
Results update automatically. Use dry air by leaving relative humidity at 0%, or include humidity for HVAC and weather-sensitive checks.
Calculated result
Formulas
Air density formulas used
Humid air
ρ = pd / (RdT) + pv / (RvT)
pv = RH x psat
Rv = 461.495 J/(kg x K)
The calculator uses the ideal gas relationship for dry air and a water-vapor correction when relative humidity is above zero. Results are suitable for early HVAC, ventilation, fan, flow, and aerodynamic estimates.
Guide
How to use this air density calculator
- Enter the air temperature.
- Enter absolute pressure. Standard sea-level pressure is 101.325 kPa.
- Enter relative humidity, or use 0% for dry air.
- Select the temperature unit: °C, °F, or K.
- Read the result, then use the graph and table to see how sensitive density is to temperature changes.
Reference
What the results mean
Density
Air density is the mass of air per unit volume. It is commonly used in kg/m3.
Constant pressure
This page assumes dry air at 1 atm, or 101.325 kPa, unless stated otherwise.
Temperature effect
At constant pressure, warmer air is less dense because it occupies more volume.
Design use
Use density for mass flow, duct flow, fan checks, drag force, buoyancy, and thermal calculations.
FAQ
Air density calculator questions
What is the density of air at 15 °C?
At 15 °C and 1 atm, dry air density is approximately 1.225 kg/m3.
What is the density of air at 25 °C?
At 25 °C and 1 atm, dry air density is approximately 1.184 kg/m3.
Does humidity change air density?
Yes. Moist air is slightly less dense than dry air at the same temperature and pressure, so humidity-sensitive work should use psychrometric data.
Related
Air property tables
Dynamic Viscosity of Air
Dynamic viscosity data for air used in fluid dynamics and heat transfer calculations.
Kinematic Viscosity of Air
Kinematic viscosity values for air across practical engineering conditions.
Specific Heat of Air
Specific heat data for air used in thermodynamic and HVAC calculations.
Thermal Conductivity of Air
Thermal conductivity values for air used in heat transfer checks.