Measured-input WBGT method
Use measured natural wet-bulb, black-globe and, where required, dry-bulb temperatures from suitable equipment following its measurement procedure.
Without solar load: WBGT = 0.7 × natural wet-bulb + 0.3 × globe
These equations are described in NIOSH publication 2016-106, section 9.3.2. All input readings must share one temperature unit and represent the same exposure. The tool accepts Celsius or Fahrenheit and converts internally.
This tool combines measured readings. It is not the same as estimating outdoor WBGT from weather data.
Worked example
Natural wet-bulb 25°C, globe 40°C and air 35°C with solar load:
0.7 × 25 + 0.2 × 40 + 0.1 × 35 = 29.0°C WBGT
Without solar load, the same wet-bulb and globe readings give 29.5°C. These are illustrative readings, not exposure limits.
Use the result in context
Heat-risk assessment also depends on workload, clothing, acclimatization, the measurement protocol and the applicable occupational guidance. No safe/unsafe rating or work-rest schedule is assigned here. Do not replace a required on-site assessment with this arithmetic tool.
Local prototype: arithmetic checked. Professional review of scope and instructions remains part of the release process.
Common questions
Where do I get the temperature readings?
Use suitable WBGT measurement equipment following its instructions. You need natural wet-bulb and black-globe readings, plus dry-bulb air temperature when there is solar load. A normal weather temperature alone is not enough.
What is the difference between the two exposure settings?
Select solar load for outdoor exposure to sunlight. Select no solar load for indoor or outdoor conditions without solar load. The formula changes and the dry-bulb input is not needed for the no-solar calculation.
Can I enter Fahrenheit?
Yes. Select Fahrenheit first, then enter all readings in that unit. Changing the unit clears inputs to prevent accidental reinterpretation.
Does the result tell me how long it is safe to work?
No. Workload, clothing, acclimatization and the applicable guidance must also be assessed. This calculator gives the unadjusted environmental WBGT only.
Original references
- NIOSH 2016-106: Occupational Exposure to Heat and Hot Environments, section 9.3.2 — equations and sensor definitions.
- OSHA: heat hazard recognition — workplace assessment context.
References checked 1 November 2026. Independent tool, not agency-endorsed.