Wet Bulb Temperature Calculator
Use this calculator to determine the Wet Bulb Temperature (WBT) based on the dry bulb (ambient) temperature and relative humidity. WBT is a critical measure for assessing heat stress risk, especially in hot and humid conditions.
Understanding Wet Bulb Temperature
The Wet Bulb Temperature (WBT) is the lowest temperature that can be reached by evaporating water into the air at constant pressure. It's a crucial indicator of heat stress because it accounts for both ambient air temperature (dry bulb temperature) and humidity. When the air is humid, less water can evaporate from surfaces, including human skin, making it harder for the body to cool itself through sweating. Therefore, a high WBT indicates a higher risk of heat-related illnesses.
Why is Wet Bulb Temperature Important?
- Heat Stress Assessment: WBT is widely used in occupational health and safety to determine safe working limits in hot environments, especially for outdoor workers, athletes, and military personnel.
- Climate Change Indicator: Rising WBTs are a significant concern with climate change, as they indicate conditions where human survival without artificial cooling becomes increasingly difficult.
- Agriculture and Livestock: High WBTs can severely impact crop yields and livestock health.
- Sports and Recreation: Event organizers use WBT to make decisions about postponing or canceling outdoor activities to protect participants.
How to Use This Calculator
- Enter Dry Bulb Temperature: Input the current ambient air temperature. You can select whether it's in Celsius (°C) or Fahrenheit (°F).
- Enter Relative Humidity: Input the current relative humidity as a percentage (0-100%).
- Click "Calculate": The calculator will then display the Wet Bulb Temperature in both Celsius and Fahrenheit.
Interpreting Your Results
The Wet Bulb Temperature provides a more accurate picture of heat stress than dry bulb temperature alone. For example, a dry bulb temperature of 35°C (95°F) with 20% humidity feels very different and poses less risk than 35°C (95°F) with 80% humidity. The latter scenario would result in a much higher WBT, indicating dangerous conditions.
- Lower WBT: Indicates more evaporative cooling potential, meaning the body can cool itself more effectively.
- Higher WBT: Indicates less evaporative cooling potential, leading to increased heat stress and a higher risk of heatstroke. A WBT above 35°C (95°F) is generally considered the theoretical limit for human survival in open air for extended periods, as the body can no longer cool itself by sweating.
Examples
Let's look at some practical examples:
Example 1: Moderate Conditions
Imagine a warm day with:
- Dry Bulb Temperature: 25°C (77°F)
- Relative Humidity: 60%
Using the calculator, the Wet Bulb Temperature would be approximately 20.6°C (69.1°F). This indicates warm but generally manageable conditions for most people.
Example 2: Hot and Humid (High Heat Stress)
Consider a very hot and muggy day:
- Dry Bulb Temperature: 35°C (95°F)
- Relative Humidity: 80%
The calculated Wet Bulb Temperature would be around 32.5°C (90.5°F). This WBT is dangerously high, indicating extreme heat stress where outdoor activity should be severely limited or avoided, and heatstroke risk is significant.
Example 3: Hot and Dry (Lower Heat Stress)
Now, a hot but dry desert-like day:
- Dry Bulb Temperature: 40°C (104°F)
- Relative Humidity: 20%
The Wet Bulb Temperature would be approximately 22.7°C (72.9°F). Despite the very high dry bulb temperature, the low humidity allows for significant evaporative cooling, resulting in a much lower WBT and reduced heat stress compared to the humid example, though hydration is still critical.