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Calcimator

Wet Bulb Globe Temperature

Calculate the Wet Bulb Globe Temperature (WBGT), the gold standard for heat stress assessment. Provides military/OSHA flag color, work-rest cycles, and hydration guidance.

Inputs

°F
°F
°F

Results

WBGT (Outdoor)

31.5 °C

Heat Flag Color

Red

WBGT (Indoor)32.2 °C
WBGT88.7 °F
Activity GuidanceLimit intense physical exertion. Rest in shade frequently.
Work/Rest Cycle20 min work / 40 min rest
Water Intake1.25 L/hr
How to Use This Calculator
  1. Measure or obtain Dry Bulb Temperature (°C) — standard air temperature in the shade.
  2. Measure Wet Bulb Temperature (°C) using a sling psychrometer or whirling hygrometer.
  3. Measure Globe Temperature (°C) using a black globe thermometer in direct sunlight.
  4. Review WBGT (Outdoor) and Flag Color: Green = low risk, Yellow = moderate, Red = high, Black = extreme.
  5. Use Work/Rest Cycle and Water per Hour (liters) to set activity guidelines for outdoor workers or athletes.

How the result changes with Wet Bulb Temperature

Wet Bulb TemperatureWBGT (Outdoor)Heat Flag Color
8.517.9 °CGreen
1723.8 °CGreen
2831.5 °CRed
3737.8 °CBlack

What each input means

Dry Bulb Temperature
Standard air temperature measured by a shaded thermometer in °C. This is the ordinary ambient temperature.
Wet Bulb Temperature
Temperature from a thermometer wrapped in a wet wick. Reflects evaporative cooling capacity — the dominant WBGT factor (70% weight).
Globe Temperature
Temperature measured inside a 150mm black copper globe. Captures radiant heat from the sun and surroundings (20% weight).

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    Dry Bulb Temperature = 35, Wet Bulb Temperature = 28, Globe Temperature = 42 = 3 input(s) provided
  2. Calculate WBGT
    WBGT = wbgtRounded
    31.5 = 31.5
  3. Calculate Heat Flag Color
    Heat Flag Color
    Red = Red
  4. Calculate WBGT
    WBGT = wbgtIndoorRounded
    32.2 = 32.2
  5. Calculate WBGT
    WBGT
    88.7 = 88.7

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