# Standard Air Density

### Standard Temperature and Pressure Conditions

Standard air density is density of air calculated at standard temperature and pressure conditions. Standard temperature and pressure conditions are used as reference points in thermodynamics of gases. Normally standard and normal temperature pressure conditions are used for specifying gas volume. Values of standard temperature and pressure depend on the organization which defines them. Usually the standard pressure is close to atmospheric pressure and standard temperature is close to room temperature value.

### Standard Air Density

Normally the standard temperature and pressure conditions are close to the atmospheric pressure and ambient temperature values. Hence the standard air density value is close to the actual air density at ambient conditions.

### Standard Air Density Calculation

Following sample calculation of air density at
standard temperature (T) = 25 0C
standard temperature (P) = 101.325 kPa
Molecular weight (MW) = 28.85 gm/mol
Universal gas constant = 8.314 J/K·mol

ρ = P×MW/(R×T) = 101.325×1000×(28.85/1000)/(8.413×(273.16+25))
ρ = 1.1792 kg/m3

Alternatively, air density calculator can be used to calculate the air density at these standard temperature and pressure conditions. As per the air density calculator,
ρ = 1.1717 kg/m3
This value matches closely with our calculation for air as an ideal gas at standard temperature and pressure conditions.