Wet Bulb Globe Temperature, or WBGT, is your body’s true heat stress scorecard. Unlike the heat index, which only considers temperature and humidity, calculating WBGT factors in the sun’s intensity, wind, and cloud cover. Think of it as a supercharged weather report designed to keep you safe. Whether you’re an athletic trainer or organizing an outdoor event, knowing how to calculate WBGT can be a game-changer for heat safety.
Our outdoor WBGT calculator helps you automatically measure the wet bulb globe temperature quickly and efficiently without any complicated input.
Calculating WBGT isn’t just for the weather geeks—it’s essential for anyone who spends time outdoors in the heat. Whether you’re using a WBGT calculator or crunching the numbers yourself, understanding this metric can help you dodge heat-related illnesses and keep your cool, no matter how hot it gets! This blog breaks down how to calculate WBGT and shows why calculating WBGT measurement is the key to keeping cool.
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Wet bulb globe temperature (WBGT) is a measure of how the weather feels, specifically, heat stress in direct sunlight. It is a perceived or apparent temperature that combines multiple environmental factors such as air temperature outdoors, relative humidity, radiant heat, and air movement to assess heat stress conditions and provide a more accurate reflection of how the human body experiences heat. According to the National Weather Service, WBGT is a better metric if you work or exercise in direct sunlight.
WBGT readings, unlike regular temperature readings, combine the effects of:
Whether you’re using a WBGT calculator or performing manual calculations, understanding the components and methods to calculate WBGT is essential to manage heat exposure effectively.
To calculate the Wet Bulb Globe Temperature (WBGT) in fahrenheit, the following formula is used:
WBGT = (0.7 * Tw) + (0.2 * Tg) + (0.1 * T)
In this WBGT formula, there are three important variables to note:
- T = Dry-bulb temperature (air temperature) in Celsius.
- Tg = Globe thermometer temperature in Celsius, measured using a black globe to assess radiant heat.
- Tw = Wet-bulb Temperature (in Celsius)
Wet bulb globe temperature is an imperative guide for maintaining a proper workload in direct sunlight as well as deterring heat strokes during an excessive heat warning. This is especially important as it differs from the heat index, which only accounts for temperature and humidity in its calculation for shaded areas.
For instance, if the WBGT is below 80, no extra precautions are necessary. But if the wet bulb globe temperature is between 80-90, the body will stress within 20-45 minutes of work or exercise in direct sunlight, with the time until stress becoming shorter as the wet-bulb globe temperature increases. If the WBGT is above 90, the body will stress in just 15 minutes and it is crucial to drink plenty of fluids and take very frequent breaks in the shade.
WBGT thermometers have been growing in popularity and usefulness, especially for youth sports and athletic programs.
States like Georgia have begun mandating the use and monitoring of WBGT for all high school outdoor athletic programs. The University Interscholastic League (UIL) has recommended Texas athletic programs to start using WBGT and moving away from heat index.
When schools and organizations follow wet bulb weather and its guidelines, they can make better decisions about:
Read more about monitoring WBGT here.
When water evaporates into the air it creates a cooling effect, but the amount of this cooling varies depending on the overall air temperature and the relative humidity.
Wet bulb temperature measures how cool the air can become through water evaporation. It’s influenced by both temperature and humidity. Essentially, it reflects the body’s ability to cool itself through sweating. Here is the equation for how to calculate wet bulb temperature:
This is a rather complex WBGT formula:
Tw = T * arctan[0.151977 * (rh% + 8.313659)^(1/2)] + arctan(T + rh%) – arctan(rh% – 1.676331) + 0.00391838 *(rh%)^(3/2) * arctan(0.023101 * rh%) – 4.686035
Here, “T” is the temperature in celsius, and “rh” represents the relative humidity.
With this final calculation, you can calculate WBGT completely.
Learn more about the differences between wet bulb temperature and wet bulb globe temperature here.
WBGT formula: (.07 * Wet-bulb Temp) + (0.2 * Globe Thermometer Temp) + (0.1 * Temperature) = Wet Bulb Globe Temperature
| Pros | Cons |
| Convenient and easy to use | Only hourly updates. A lot can change in an hour |
| No site-specific data. Pulls data from the National Weather Service, which could be up to 25 miles away. | |
| Often shows inaccurate measurements. |
| Pros | Cons |
| Portable | Too manual: Lacks automated WBGT data logging features |
| Durable; Built for outdoors | Inaccurate readings: Small black bulb sensor causes massive spikes in WBGT readings |
| Lacks radiation shield, leading to erroneously high WBGT readings |
Okay, that was a lot. But don’t panic!
You don’t really need a WBGT calculator or a formula to calculate the WBGT accurately. There are much faster and much, much easier ways to calculate wet bulb globe temperature.
For regular users of wet bulb globe temperature calculations and regulations, it’s best to use an integrated WBGT calculator service or a WBGT device for up-to-date information.
Perry Weather offers weather monitoring software and hardware to simplify the entire WBGT monitoring process.
Learn more about how Perry Weather tracks the wet bulb globe temperature and how it can help you here
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The wet bulb globe temperature (WBGT) can be measured with on-site weather stations, handheld devices known as WBGT monitors, or online WBGT and weather monitoring apps. These tools calculate the temperature, humidity, and sunlight to compute the WBGT index.
Wet bulb globe temperature readings can be taken using a WBGT monitoring device like a weather monitoring station or a handheld monitor. Readings must be taken by an athletic director/administrator or medical personnel overseeing the event.
The WBGT should be monitored throughout the event and readings must be taken every 20 to 30 minutes, with athletic activities being adjusted accordingly. Participation modifications must be communicated to the coaching staff before and during practice.
Regularly monitoring the WBGT levels allows coaches and athletic trainers to adjust training schedules, implement hydration protocols, and make informed decisions to protect athletes from high temperature and heat-related risks. Tracking the WBGT is crucial to protect athletes’ health and safety during outdoor practices, games, and events.
WBGT should be measured regularly, especially during periods of high heat or physical activity. The frequency depends on the specific situation and guidelines.
While some apps provide estimates of WBGT, WBGT monitors and weather stations like Perry Weather offer more accurate and reliable measurements.
The streamlined approach uses the latest technology to provide a multitude of industries with real-time updates to temperature, relative humidity, wet bulb temperature, globe thermometer temperature, and WBGT.
Using Perry Weather Weather Station software, you don’t need a manual WBGT calculator and it only takes the click of a button to receive consistently calculated wet bulb globe temperatures no matter where you are and ensure your people are safe in every job, every game, and every season.
Track and record WBGT, heat stress, and much more. Sign up for your two-week free trial today!
