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
| Field | What to enter |
|---|---|
| Air temperature | Units: °C, °F, K |
| Relative 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) |
|---|---|
| 12.5 | 6.5851 |
| 18.75 | 9.6131 |
| 25 | 13.7807 |
| 31.25 | 19.4232 |
| 37.5 | 26.9473 |
| 50 | 49.671 |
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
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.
Frequently asked questions
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.