# Air Density Calculator

URL: https://speedycalculator.com/calculators/physics/air-density/
Last updated: 2026-10-30

> The air density calculator finds the density of dry or humid air from the pressure, temperature and relative humidity or dew point, treating air as a mixture of dry air and water vapour.

## Inputs

- Air pressure (hPa, kPa, inHg, mmHg, psi, atm)
- Air temperature (°C, °F, K)
- Humidity given as
- Relative humidity (%)
- Dew point (°C, °F, K)

## Results

- Vapour pressure
- Air density
- Dry air at the same p and T

## 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)
```

## Explanation

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

FieldWhat to enterAir pressureUnits: hPa, kPa, inHg, mmHg, psi, atmAir temperatureUnits: °C, °F, KHumidity given asChoose one: Relative humidity, Dew pointRelative humidity (%)A numberDew pointUnits: °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)506.630.6086759.940.91481,013.251.22111,266.561.52731,519.881.83362,026.52.4461

## 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.

## FAQ

**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.


## Sources

- [NOAA / National Weather Service – Weather calculators](https://www.weather.gov/epz/wxcalc)
- [Vaisala – Humidity conversion formulas](https://www.vaisala.com/en/lp/humidity-conversion-formulas)
- [NIST – Fundamental physical constants](https://physics.nist.gov/cuu/Constants/)