Enter your air temperature and relative humidity to calculate the wet bulb temperature — the lowest temperature achievable through evaporative cooling. Results include wet bulb temperature, dew point, and a heat stress category so you can assess real-world thermal comfort and safety.
Wet Bulb Temperature
--
Dew Point
--
WBGT Estimate (Simplified)
--
Heat Stress Category
--
Wet bulb temperature is the lowest temperature that can be achieved through evaporative cooling of water. It is measured by a thermometer wrapped in a wet cloth, and unlike dry bulb temperature, it accounts for humidity in the air. The higher the humidity, the less cooling occurs via evaporation, and the closer the wet bulb temperature is to the dry bulb temperature.
This calculator uses the Stull (2011) formula: Tw = T × arctan(0.151977 × √(RH + 8.313659)) + arctan(T + RH) − arctan(RH − 1.676331) + 0.00391838 × RH^1.5 × arctan(0.023101 × RH) − 4.686035, where T is air temperature in °C and RH is relative humidity in percent. This empirical formula is accurate for typical atmospheric conditions.
Dry bulb temperature is the standard air temperature measured by a regular thermometer unaffected by moisture. Wet bulb temperature accounts for humidity and evaporative cooling — it is always equal to or lower than the dry bulb temperature. The greater the difference between the two, the drier the air.
WBGT is a composite index used to estimate heat stress in direct sunlight. It incorporates wet bulb temperature, globe temperature (radiant heat), and dry bulb temperature using the formula: WBGT = 0.7×Tw + 0.2×Tg + 0.1×T. This calculator provides a simplified outdoor WBGT estimate assuming globe temperature approximates air temperature, useful for a quick assessment.
A wet bulb temperature of around 35°C (95°F) is considered the theoretical upper limit for human survivability, as the body can no longer cool itself through sweating under those conditions. For outdoor activity and labor, wet bulb temperatures above 28°C indicate significant heat stress risk. Comfortable conditions typically fall below 18°C wet bulb.
No, they are related but different metrics. The Heat Index (apparent temperature) reflects how hot it feels to the human body based on temperature and humidity. Wet bulb temperature is a physical measurement representing the cooling limit of evaporation. Both increase with higher humidity, but wet bulb temperature is a more scientifically precise measure used in meteorology and occupational safety.
At 25°C and 40% relative humidity, the wet bulb temperature is approximately 15.9°C. This represents a comfortable outdoor condition with a good evaporative cooling margin, meaning the body can effectively regulate heat through perspiration.
High wet bulb temperatures reduce the body's ability to cool down through sweating, significantly increasing the risk of heat exhaustion and heat stroke. OSHA and sports medicine organizations use wet bulb and WBGT thresholds to guide work-rest cycles, activity modifications, and emergency protocols for outdoor workers and athletes during hot and humid conditions.