How the Air Converter Works
The Air Converter divides air mass by air density at your conditions. The default 0.001225 kg/L (1.225 kg/m³) is dry air at sea level and 15°C (59°F) in the International Standard Atmosphere (ISA).
Note temperature, pressure and humidity
Warm, high-altitude or humid air weighs less per liter.
Get the density
Read the altitude table below or calculate ρ = P ÷ (287.05 × T).
Enter mass and density
Type the air mass in kg and the density in kg/L in the number box.
Read the liters
Divide by 1,000 for cubic meters.
Air Converter Formula
The dry air density formula is ρ = P ÷ (Rd × T), with Rd = 287.05 J/(kg·K). Humid air uses a virtual temperature correction.
- P
- Absolute air pressure, Pa
- T
- Air temperature, K
- Rd
- Specific gas constant for dry air
Worked Examples
- Sea level, 15°C: 101,325 ÷ (287.05 × 288.15) = 1.225 kg/m³, so 1 kg fills 816 L.
- Room at 20°C: 101,325 ÷ (287.05 × 293.15) = 1.204 kg/m³.
- Room air mass: a 5 × 4 × 2.5 m room holds 50 m³ × 1.204 = 60.2 kg of air.
Air Converter Conversion Table
Air density drops from 1.225 kg/m³ at sea level to 0.414 kg/m³ at 10,000 m (32,808 ft). The table lists ISA air density by altitude.
| Altitude | Temperature (ISA) | Pressure (hPa) | Density (kg/m³) | Liters per 1 kg |
|---|---|---|---|---|
| 0 m (0 ft) | 15.0°C | 1,013.3 | 1.2250 | 816 |
| 500 m (1,640 ft) | 11.8°C | 954.6 | 1.1673 | 857 |
| 1,000 m (3,281 ft) | 8.5°C | 898.8 | 1.1117 | 900 |
| 1,500 m (4,921 ft) | 5.3°C | 845.6 | 1.0581 | 945 |
| 2,000 m (6,562 ft) | 2.0°C | 795.0 | 1.0066 | 993 |
| 3,000 m (9,843 ft) | -4.5°C | 701.2 | 0.9093 | 1,100 |
| 5,000 m (16,404 ft) | -17.5°C | 540.5 | 0.7364 | 1,358 |
| 8,000 m (26,247 ft) | -37.0°C | 356.5 | 0.5258 | 1,902 |
| 10,000 m (32,808 ft) | -50.0°C | 264.4 | 0.4135 | 2,418 |
| 11,000 m (36,089 ft) | -56.5°C | 227.0 | 0.3639 | 2,748 |
What is an Air Converter?
An Air Converter is a calculator that converts a mass of air into volume using air density for temperature, pressure and humidity.
Dry air is 78.08% nitrogen, 20.95% oxygen, 0.93% argon and 0.04% carbon dioxide by volume. The average molar mass is 28.965 g/mol.
Water vapor (18.02 g/mol) is lighter than dry air. Humid air at the same temperature and pressure is less dense than dry air, which lowers engine power and aircraft lift on humid days.
What are the Uses of an Air Converter?
There are 5 main uses of an Air Converter.
HVAC sizing
Engineers convert kg/s of air into m³/h for fans and ducts.
Aircraft performance
Pilots check density altitude for take-off distance.
Engine tuning
Tuners convert air mass flow into displacement volume.
Compressed air
Plants convert free air delivery into mass flow.
Physics classes
Students weigh the air in a classroom.