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 humid or wet air temperature measured with a wet thermometer. And the air pressure. The dry temperature is warmer than the wet temperature. The humidity can be calculated from these three 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

Psychrometric humidity describes the moisture content of the air and is a key parameter in meteorology, climate control, and various industrial and scientific applications. It indicates how much water vapor is contained in the air and how this affects temperature, pressure, and other environmental conditions. The psychrometric approach combines the physical properties of air and water to provide a comprehensive understanding of humidity.

The tool used to analyze psychrometric humidity is the psychrometer, a measuring device consisting of two thermometers, a dry thermometer and a wet thermometer. The dry thermometer measures the current air temperature, while the wet thermometer, due to evaporative cooling, indicates a lower temperature. The difference between the two readings, known as the psychrometric difference, allows for the calculation of relative humidity. This method is based on the principle that the rate of water evaporation depends on the humidity. The drier the air, the greater the evaporation and thus the cooling of the wet thermometer.

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