Absolute Humidity Calculator

Work out absolute humidity instantly with clear inputs, formula shown and shareable results.

About Absolute Humidity Calculator

Absolute humidity is the actual mass of water vapour per cubic metre, obtained by applying the ideal gas law to the vapour partial pressure. Air at 25 C and 60% relative humidity holds 19 hPa of vapour, about 13.8 g/m3, with a dew point near 16.7 C. Unlike relative humidity, it does not change when the air is heated.

Formulas

Vapour pressure

ea = RH / 100 x es(T)

Absolute humidity

AH = ea x M(water) / (R x T)

Worked example

With the default values below, Absolute Humidity Calculator returns Absolute Humidity of 13.779. Change any input above and every figure here is recalculated in your browser.

Inputs used

Air temperature: 25 C
Relative humidityaccepts 0–100 %: 60 %

Results

Absolute Humidity: 13.779 g/m3
Actual Vapour Pressure: 18.960 hPa
Mixing Ratio: 11.861 g/kg
Dew Point: 16.69 C

Step by step

1Values used
2Vapour pressure
3Absolute humidity
4Absolute Humidity= 13.779 g/m3
5Actual Vapour Pressure= 18.960 hPa
6Mixing Ratio= 11.861 g/kg
7Dew Point= 16.69 C

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does absolute humidity matter for drying and preservation?

Because moisture transfer depends on the vapour pressure difference, which relates to absolute rather than relative content.

What is the mixing ratio?

Grams of vapour per kilogram of dry air. Meteorologists prefer it because it is conserved as air rises and cools.