# Absolute Humidity Calculator

URL: https://speedycalculator.com/calculators/physics/absolute-humidity/
Last updated: 2026-10-30

> The absolute humidity calculator finds the mass of water vapour per cubic metre of air from the temperature and relative humidity, along with the saturation and actual vapour pressures.

## Inputs

- Air temperature (°C, °F, K)
- Relative humidity (%)

## Results

- Saturation vapour pressure
- Actual vapour pressure
- Absolute humidity
- Maximum at this temperature

## Formula

```
e_s = 6.112·exp(17.62T/(243.12 + T)) hPa,  e = RH·e_s,  AH = 216.7·e/(T + 273.15) g/m³
```

## Explanation

Absolute humidity tells how much water the air actually holds, independent of temperature. Warm tropical air can hold over 25 g/m³; cold winter air only a few grams – which is why heated indoor air feels so dry.

### How to use the Absolute Humidity Calculator

- **Air temperature**
- **Relative humidity (%)**

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 and relative humidity.

### Inputs explained

FieldWhat to enterAir temperatureUnits: °C, °F, KRelative humidity (%)A number

### What each result means

- **Saturation vapour pressure** = 6.112×exp(17.62×([Air temperature])÷(243.12 + ([Air temperature])))
- **Actual vapour pressure** = [Relative humidity (%)]÷100×[Saturation vapour pressure]
- **Absolute humidity** = 216.7×[Actual vapour pressure]÷([Air temperature] + 273.15)
- **Maximum at this temperature** = 216.7×[Saturation vapour pressure]÷([Air temperature] + 273.15)

### Example values

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

Air temperature (°C)Absolute humidity (g/m³)12.56.585118.759.61312513.780731.2519.423237.526.94735049.671

## Worked example

Inputs — Air temperature: 25 °C; Relative humidity (%): 60.

Results — Saturation vapour pressure = 31.6006 hPa; Actual vapour pressure = 18.9603 hPa; **Absolute humidity = 13.7807 g/m³**; Maximum at this temperature = 22.9678 g/m³.

## Key terms

- **Vapour pressure**: Partial pressure of water vapour in air.

## FAQ

**How is absolute humidity different from relative humidity?**
AH is the actual water content; RH is the fraction of the maximum possible.

**Why is winter indoor air dry?**
Cold outdoor air holds little water, so when heated its RH drops.

**What is a typical value?**
5–15 g/m³ in temperate climates.

**Which formula is used?**
The Magnus approximation, accurate within 0.1% from −45 to 60 °C.


## 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)