Wet Bulb Calculator

°F °C
Temperature is in °F (Only accurate for temperature between -4°F and 122°F)
Relative Humidity Percent (Only accurate for percentages between 5% and 99%)
Wet-Bulb Temperature:


Wet Bulb Temperature is calculated based on R. Stull (2011) equation 3:41

Stull, Roland 2011: Wet-Bulb Temperature from Relative Humidity and Air Temperature Journal of Applied Meteorology and Climatology, 50 (11), 2267–2269

Other References:

Alduchov, O. A., and R. E. Eskridge, 1996: Improved Magnus' form approximation of saturation vapor pressure. J. Appl. Meteor., 35, 601–609.
August, E. F., 1828: Ueber die Berechnung der Expansivkraft des Wasserdunstes. Ann. Phys. Chem., 13, 122–137.
Magnus, G., 1844: Versuche über die Spannkräfte des Wasserdampfs. Ann. Phys. Chem., 61, 225–247.

Human body loses heat through 4 mechanisms: first is radiation emission since human skin and hair emit longwave radiation at human body skin temperature to surrounding environment; the 2nd mechanism is convection, when air molecules (i.e. wind) move thought human body and bring heat energy away; the 3rd mechanism is conduction in which human body loses heat to surrounding lower temperature objects (for example, air, or his wet clothes). The 4th one is evaporative cooling, which is when human being is in wet clothes or sweats, evaporation occurs and thus takes energy from body in form of latent heat. When in wet, evaporative cooling would be combined the other processes (radiation, convection, and conduction) to significantly reduce body temperature.
Tw is not measured, forecasted, and reported by national weather service (NWS), the nation’s operational, free weather service. Runners, construction workers, law enforcement (i.e., policeman) who would present in cold environment, may need to have this Tw information, with adequate education of how to use this information, to prevent cold-weather induced medical emergencies, such as hypothermia and frostbite.

R&D is ongoing. For more information, contact sgweather.webservice@gmail.com