For indoor environments, the meter does not use the dry-bulb temperature since the globe and the dry-bulb should be equal without radiant heat. The globe temperature is used since it will also detect non-solar radiant heat sources if they are present. The equation weighs the wet-bulb 70% and the globe 30% of the weighted average: (WB)
The WBGT combines the effect of the four main thermal components affecting heat stress: air temperature, humidity, air velocity, and radiant heat (included in outdoor) as measured by the dry bulb (Tdb), natural wet bulb (Tnwb), and globe temperatures (Tg). For indoor conditions (or outdoors without solar load (Tdb), e.g., cloudy or shaded), WBGT values can be determined from the following equation: (WB)
| Variable | Unit |
|---|---|
| WBGT | Temperature F |
| tnwb | natural wet bulb temperature F |
| tg | globe temperature F |