Absolute Humidity
Calculator
Results
- Absolute humidity (g/m³)
- 13.787809
- Vapour pressure (hPa)
- 18.971505
Weather results
| Absolute humidity (g/m³) | 13.787809 |
| Vapour pressure (hPa) | 18.971505 |
formula-map diagram
- Absolute humidity (g/m³)
- 13.787809
- Vapour pressure (hPa)
- 18.971505
Weather relationship
Formula
AH = e ÷ (Rv × T), Rv = 461.5 J/(kg·K), e = es(T) × RH÷100= 13.787809475862
Note
This is a simplified model: it applies the published standard formula to the numbers you entered and ignores local terrain, radiation, precipitation type and instrument error. Wind chill is the 2001 NWS/Environment Canada regression, valid at or below 10 °C with wind at or above 4.8 km/h; the heat index is the Rothfusz regression, reliable above about 27 °C; dew point uses the Magnus approximation (a = 17.27, b = 237.7 °C) over liquid water; wet bulb uses Stull's approximation at standard sea-level pressure; pressure and density altitude assume the International Standard Atmosphere and dry air. Do not use these results for aviation, structural or safety decisions without an official forecast or a qualified professional.
More in Weather and climate
See all →Frequently asked questions
How is absolute humidity different from relative humidity?+
Absolute humidity is the actual mass of water vapor present per unit volume of air (commonly grams per cubic metre), independent of temperature, while relative humidity is a percentage comparing that amount to the maximum the air could hold at its current temperature.
Why does absolute humidity not change when air is heated or cooled (without adding or removing moisture)?+
Absolute humidity measures the actual quantity of water vapor molecules in the air, which doesn't change just because the air's temperature changes. Only relative humidity changes with temperature, since the air's capacity to hold moisture, not the moisture itself, is what shifts.
What inputs does the calculator need to find absolute humidity?+
Typically air temperature and either relative humidity or dew point. From these, the actual water vapor pressure is calculated and then converted into a mass-per-volume figure using the ideal gas law relationship for water vapor.
Why does absolute humidity matter for things like mold risk or drying processes?+
Processes like evaporative drying, condensation on cold surfaces, and mold growth respond to the actual quantity of moisture in the air, not to a relative percentage. Two rooms at the same relative humidity but different temperatures can have very different absolute moisture loads and therefore different real-world drying or condensation behavior.
Can absolute humidity be higher in a cold place than a hot place at 100% relative humidity?+
No, because 100% relative humidity at a lower temperature corresponds to a much lower total water vapor capacity than 100% at a higher temperature. Hot saturated air always carries more absolute moisture than cold saturated air.