Air density affects aircraft lift, engine power, ball flight and wind turbine output. Surprisingly, humid air is lighter than dry air, because water molecules (18 g/mol) weigh less than nitrogen and oxygen (~29 g/mol).
How to use the Air Density Calculator
- Air pressure
- Air temperature
- Humidity given as
- Relative humidity (%)
- Dew point
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the air pressure, temperature and humidity (as relative humidity or dew point). Set 0% humidity for dry air.
Inputs explained
| Field | What to enter |
|---|---|
| Air pressure | Units: hPa, kPa, inHg, mmHg, psi, atm |
| Air temperature | Units: °C, °F, K |
| Humidity given as | Choose one: Relative humidity, Dew point |
| Relative humidity (%) | A number |
| Dew point | Units: °C, °F, K |
What each result means
- Air density = ([Air pressure] – [Vapour pressure])÷(287.058×([Air temperature] + 273.15)) + [Vapour pressure]÷(461.495×([Air temperature] + 273.15))
- Dry air at the same p and T = [Air pressure]÷(287.058×([Air temperature] + 273.15))
Example values
How the main result changes when Air pressure changes and everything else stays at the example values above:
| Air pressure (hPa) | Air density (kg/m³) |
|---|---|
| 506.63 | 0.6086 |
| 759.94 | 0.9148 |
| 1,013.25 | 1.2211 |
| 1,266.56 | 1.5273 |
| 1,519.88 | 1.8336 |
| 2,026.5 | 2.4461 |
Formula
ρ = p_d/(R_d·T) + p_v/(R_v·T), p_v = RH·e_s(T), p_d = p − p_v, R_d = 287.058, R_v = 461.495 J/(kg·K)
Worked example
Inputs — Air pressure: 1,013.25 hPa; Air temperature: 15 °C; Humidity given as: Relative humidity; Relative humidity (%): 50.
Results — Vapour pressure = 850.83601 Pa; Air density = 1.22109 kg/m³; Dry air at the same p and T = 1.22498 kg/m³.
Key terms
- Partial pressure
- Pressure a gas component would exert alone.
Frequently asked questions
What is standard air density?
1.225 kg/m³ at 15 °C and 1013.25 hPa.
Is humid air heavier?
No – it is slightly lighter.
How does altitude change density?
It falls by about 9–10% per 1,000 m near sea level.
Why do pilots care?
Lower density reduces lift and engine power.