Psychrometric Humidity Calculator

Here the air humidity can be calculated from a psychrometric measurement. To do this you need three measurements: the dry air temperature, measured with a normal thermometer. The wet air temperature measured with a wet thermometer. And the air pressure. The humidity can be calculated from these values ​​using an approximate formula.

Dry air temperature Tn: °C
Wet air temperature Tw: °C
Air pressure P: hPa
Relativ humidity H: %

The formula after WMO (2012): Guide to Meteorological Instruments and Methods of Observation, WMO-No. 8, © World Meteorological Organization, Seventh edition, 2012 from the source Biosystems Engineering Laboratory Osnabrück is:

H = ((1.0016+3.15/1000000*P-0.074/P)*6.112*exp((17.62*Tw)/(243.12+Tw)) - 6.53/10000*(1+9.44/10000*Tw)*P*(Tn-Tw)) / ((1.0016+3.15/1000000*P-(0.074/P))*6.112*exp((17.62*Tn)/(243.12+Tn)))*100

Physics commonly uses SI units. Here is a calculator to convert lengths, temperature, pressure, speed and other units.

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