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Absolute humidity

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Sergiy A. Gritcsenko edited this page Nov 4, 2016 · 12 revisions

###Relative humidity (RH) The ratio of the actual amount of water vapour in the air to the amount it could hold when saturated expressed as a percentage or the ratio of the actual vapour pressure to the saturation vapour pressure expressed as a percentage.

![](http://planetcalc.com/cgi-bin/mimetex.cgi?RH=100 \cdot \frac{e}{e_w})

###Absolute humidity The mass of water vapour in a unit volume of air. It is a measure of the actual water vapour content of the air.

From relative humidity and saturation vapour pressure we can find actual vapour pressure.

![](http://planetcalc.com/cgi-bin/mimetex.cgi?e= e_w \frac{RH}{100})

Then we can use the general law of perfect gases

where

In our case this is

water molar mass is

and we've got

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