What this calculator does

This WBGT calculator provides an estimated Wet Bulb Globe Temperature from air temperature and relative humidity. WBGT is widely used as a heat-stress screening metric because it is more relevant than simple air temperature in sunny or high-load outdoor conditions.

Unlike heat index, WBGT is meant to reflect the broader environmental burden on the body. Full WBGT considers wet-bulb temperature, globe temperature, and dry-bulb temperature, which means humidity, radiant heat, airflow, and sunlight all matter. This page uses an approximation, so it should be interpreted as a screening tool rather than a substitute for a measured globe-temperature instrument.

Inputs explained

• Air temperature: Enter the ambient dry-bulb temperature.
• Relative humidity: Enter the moisture percentage used to estimate the vapor pressure term.
• Unit selector: The page converts to Celsius internally because the approximation formula is expressed in metric form.

How it works / method

The engine uses a Bureau of Meteorology-style empirical estimate that converts temperature and humidity into vapor pressure and then applies a linear WBGT approximation. This is useful when you need a fast heat-stress estimate but do not have a dedicated WBGT meter or a full set of radiation and wind observations. Because it is an estimate, it should sit alongside direct weather and exposure context, not replace them.

Formula used

T is air temperature in C and e is water-vapor pressure in hPa. The page does not solve the full globe-temperature physics, so the result is an estimated WBGT rather than an instrument-grade WBGT observation.

Step-by-step example

Suppose the air temperature is 31 C and the relative humidity is 65 percent. The estimate helps frame how physically demanding those conditions may feel outdoors.

1. Enter 31 for air temperature.
2. Enter 65 for relative humidity.
3. The calculator converts humidity to vapor pressure and then estimates WBGT.
4. If the resulting value is high, the environment may warrant rest breaks, hydration, shade, or reduced exertion.
5. The same dry-bulb temperature with lower humidity usually produces a noticeably lower estimate.

Use cases

• Screening outdoor work or sports conditions before using more formal heat-safety guidance.
• Comparing sun-exposed hot-weather days when heat index alone may understate environmental stress.
• Supporting plain-language safety communication in schools, camps, and field operations.
• Understanding why solar load and humidity can make heat management more complex than a simple thermometer reading suggests.

Assumptions and limitations

• This page estimates WBGT and does not replace measured globe temperature or full instrument-based WBGT.
• The approximation does not directly model local radiation, cloud cover, wind profile, clothing, or metabolic work rate.
• Thresholds vary by region, acclimatization, and the governing guidance for the activity or workplace.
• Any heat-stress index should be used with hydration, exposure time, and symptom monitoring, not in isolation.

If you only want a shaded comfort index, use heat index instead. If you need compliance or formal exposure management, use measured WBGT and the relevant organizational standard.

Sources & references

• NOAA National Weather Service - Heat index guidance
• NOAA National Weather Service - Wind chill chart and formula
• NOAA National Weather Service - Wet Bulb Globe Temperature overview
• Bureau of Meteorology - Apparent temperature background
• Bureau of Meteorology - Apparent temperature glossary
• Environment and Climate Change Canada - Humidex guidance
• Schema.org - FAQPage and WebApplication vocabulary