Occupational Safety and Health Administration OSHA

OSHA Outdoor WBGT Calculator

This calculator estimates outdoor wet bulb globe temperature (WBGT) from standard meteorological inputs. It uses the Kasten-Czeplak algorithm to estimate the clear sky solar irradiance (Sandia, 2012). It then estimates WBGT via the heat and mass transfer algorithm of Liljegren et al. (2008).

This product includes software produced by UChicago Argonne, LLC under Contract No. DE-AC02-06CH11357 with the Department of Energy. See copyright notice at the bottom of this page.

Please provide the following:

Date in MM/DD/YYYY format:
Local time in HH:MM format (24-hour time; please enter an hour between 00 and 23):

Time zone:
Latitude in decimal degrees (0 to 90):

Longitude in decimal degrees (0 to 180):

Air (dry bulb) temperature (degrees Fahrenheit):
Relative humidity (%):
Wind speed (mph):
Barometric pressure (inches of Mercury [Hg]). Defaults to 29.92 inches Hg (1 atmosphere) if not specified:
Is the wet bulb temperature known?

If yes: Enter the wet bulb temperature (degrees Fahrenheit).

Is the solar irradiance (W/m2) known?

If yes: Enter the solar irradiance (W/m2).


Estimated WBGT from calculated solar irradiance (will be blank if the user supplied the solar irradiance):

WBGT if in direct sunlight (assumes no clouds and a clear sky with an estimated solar irradiance of W/m2).

WBGT if in shade (assumes a sheltered/shady outdoor location with solar irradiance = 0 W/m2).

*** NOTE *** If clouds were present, the WBGT likely was between the "direct sunlight" and "shade" estimates given above. This calculator does not attempt to adjust the WBGT for cloud cover. The reason is that such an adjustment depends on many factors--e.g., cloud thickness, cloud height, number of cloud layers, and whether or not the cloud was blocking the sun--that are difficult or impossible to determine in retrospect.

Estimated WBGT from user-specified solar irradiance (will be blank if no solar irradiance was provided):
WBGT assuming solar irradiance of W/m2.
Heat Index:
Copyright Notice

Original WBGT software Copyright © 2008, UChicago Argonne, LLC

All Rights Reserved WBGT, Version 1.1
James C. Liljegren
Decision & Information Sciences Division


Sandia National Laboratories. 2012. Sandia Report SAND2012-2389: Global horizontal irradiance clear sky models: implementation and analysis.

Liljegren JC, Carhart RA, Lawday P, Tschopp S, Sharp R. Modeling the wet bulb globe temperature using standard meteorological measurements. Journal of Occupational and Environmental Hygiene 2008;5(10):645-655.

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