# Mixing Ratio of Air Calculator

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

> The mixing ratio calculator finds the mass of water vapour per kilogram of dry air, the saturation mixing ratio and the relative humidity from the temperature, dew point and pressure.

## Inputs

- Air temperature (°C, °F, K)
- Dew point (°C, °F, K)
- Air pressure (hPa, kPa, inHg, mmHg, psi, atm)

## Results

- Vapour pressure
- Saturation vapour pressure
- Mixing ratio
- Saturation mixing ratio
- Relative humidity

## Formula

```
e = e_s(T_d),  w = 621.97·e/(p − e) g/kg,  w_s = 621.97·e_s(T)/(p − e_s(T)),  RH ≈ e/e_s(T)
```

## Explanation

Meteorologists track moisture with the mixing ratio because it doesn't change when air rises or sinks (until clouds form). It is plotted on every Skew-T diagram used in weather forecasting.

### How to use the Mixing Ratio of Air Calculator

- **Air temperature**
- **Dew point**
- **Air pressure**

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 temperature, dew point and air pressure.

### Inputs explained

FieldWhat to enterAir temperatureUnits: °C, °F, KDew pointUnits: °C, °F, KAir pressureUnits: hPa, kPa, inHg, mmHg, psi, atm

### What each result means

- **Vapour pressure** = 6.112×exp(17.62×([Dew point])÷(243.12 + ([Dew point])))
- **Saturation vapour pressure** = 6.112×exp(17.62×([Air temperature])÷(243.12 + ([Air temperature])))
- **Mixing ratio** = 621.97×[Vapour pressure]÷([Air pressure]÷100 - [Vapour pressure])
- **Saturation mixing ratio** = 621.97×[Saturation vapour pressure]÷([Air pressure]÷100 - [Saturation vapour pressure])
- **Relative humidity** = [Vapour pressure]÷[Saturation vapour pressure]×100

### Example values

How the main result changes when **Air temperature** changes and everything else stays at the example values above:

Air temperature (°C)Mixing ratio (g/kg)12.510.623918.7510.62392510.623931.2510.623937.510.62395010.6239

## Worked example

Inputs — Air temperature: 25 °C; Dew point: 15 °C; Air pressure: 1,013.25 hPa.

Results — Vapour pressure = 17.01672 hPa; Saturation vapour pressure = 31.60057 hPa; **Mixing ratio = 10.62391 g/kg**; Saturation mixing ratio = 20.02202 g/kg; Relative humidity = 53.8494 %.

## Key terms

- **Mixing ratio**: Mass of water vapour per mass of dry air.

## FAQ

**What is a typical mixing ratio?**
5–20 g/kg near the surface in mid-latitudes.

**Why is it conserved?**
It counts water per dry air, so expansion doesn't change it.

**How does it differ from specific humidity?**
Specific humidity is per kilogram of moist air.

**What is the saturation mixing ratio?**
The maximum mixing ratio at that temperature and pressure.


## 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)