What Is the Density of Air in kg/m³?

The density of air at sea level, at 15°C, is about

1,225 kg/m³

Air Density: a Highly Variable Value

Unlike solids and liquids, the density of air (and gases in general) varies significantly with temperature, pressure, and altitude. The standard reference value, 1.225 kg/m³, refers to sea-level conditions and 15°C as defined by the International Standard Atmosphere (ISA). As altitude increases, air becomes progressively less dense, because atmospheric pressure decreases.

The Conversion Formula

Air density can be estimated using the ideal gas law, but for practical purposes reference tables based on altitude and temperature are often used. The weight of air in a volume is still calculated as for any material:

weight (kg) = volume (m³) × air density (kg/m³)

For example, a 50 m³ room contains air that weighs about:

50 m³ × 1.225 kg/m³ ≈ 61.25 kg

Practical Examples

  • Sea level, 15°C: ≈ 1.225 kg/m³ (standard ISA value)
  • Sea level, 25°C: ≈ 1.184 kg/m³ (warm air is less dense)
  • 2,000 m altitude, 15°C: ≈ 1.007 kg/m³ (about 18% less than sea level)
  • 8,000 m altitude (cruising altitude of many aircraft): ≈ 0.526 kg/m³, less than half the value at ground level

When This Information Is Needed

Air density is fundamental in aviation (for calculating an wing's lift, which directly depends on the density of the air passing over it), in meteorology, in sports (aerodynamic drag in cycling or athletics varies with air density), and in HVAC systems for sizing ventilation systems.

Other Density Conversions

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