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.

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*T_w)/(243.12+T_w)) - 6.53/10000*(1+9.44/10000*T_w)*P*(T_n-T_w)) / ((1.0016+3.15/1000000*P-(0.074/P))*6.112*exp((17.62*T_n)/(243.12+T_n)))*100

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

Dry air temperature T_n:		°C
Wet air temperature T_w:		°C
Air pressure P:		hPa
Relativ humidity H:		%