Introduction
Wet-bulb temperature tells you how well your body can cool itself through sweat. It combines air temperature and humidity into one number. When the air holds a lot of moisture, sweat does not evaporate as fast, and you feel much hotter. A high wet-bulb temperature means a higher risk of heat stroke and other heat-related illness.
This wet-bulb calculator takes your air temperature and relative humidity and gives you the wet-bulb temperature in Celsius, Fahrenheit, and Kelvin. It also calculates the dewpoint temperature and shows you a heat stress rating so you can see how dangerous the conditions are. If you know your local station pressure, you can enter it under Advanced Options for a more precise result.
The calculator uses the Stull (2011) formula by default. When you add station pressure, it switches to a psychrometric method that accounts for your elevation. Both methods are shown step by step so you can follow the math. A chart plots how wet-bulb and dewpoint change as humidity rises, making it easy to see how moisture in the air affects heat stress.
How to Use Our Wet Bulb Calculator
Enter your air temperature and humidity below. The calculator will give you the wet-bulb temperature, dewpoint temperature, and heat stress level in seconds.
Dry-Bulb (Air) Temperature — Type the current air temperature shown on a regular thermometer. Pick your unit: °C, °F, or K. The calculator will convert it for you. If you need help switching between Celsius and Fahrenheit, try our Celsius to Fahrenheit calculator.
Relative Humidity — Type the relative humidity as a percentage from 0 to 100. You can find this value from a local weather report or a hygrometer.
Station Pressure (Optional) — Click "Advanced Options" if you know your local station pressure. This is the actual air pressure at your location, not the sea-level adjusted value. Adding pressure improves accuracy. If you leave it blank, the calculator uses the standard Stull formula instead.
Press the Calculate Wet-Bulb Temperature button to see your results. You will get the wet-bulb and dewpoint temperatures in °C, °F, and K, a color-coded heat stress rating, a full step-by-step solution, and a chart that shows how wet-bulb and dewpoint change across humidity levels.
What Is Wet-Bulb Temperature?
Wet-bulb temperature is the lowest temperature air can reach through evaporation alone. Think of how your skin feels cool when you step out of a pool on a hot day. That cooling happens because water evaporates off your body. Wet-bulb temperature measures exactly how much cooling evaporation can provide in the current air.
To find it, you wrap a wet cloth around a thermometer. As water evaporates from the cloth, the thermometer drops. When the air is dry, a lot of water evaporates and the temperature drops a lot. When the air is humid, less water evaporates and the temperature barely drops at all. At 100% humidity, the wet-bulb temperature equals the regular air temperature because no evaporation can happen.
Why Wet-Bulb Temperature Matters
Your body cools itself by sweating. Sweat evaporates off your skin and carries heat away. But this only works when the air can accept more moisture. Wet-bulb temperature tells you how well this process works. A high wet-bulb reading means the air is too warm and too humid for sweat to cool you down. The heat index calculator is another useful tool that estimates how hot it actually feels by combining temperature and humidity.
At a wet-bulb temperature of 35°C (95°F), the human body can no longer cool itself through sweating. This is considered the upper survival limit for prolonged exposure, even for healthy people resting in shade. Below that threshold, rising wet-bulb values still pose serious risks. Heat exhaustion and heatstroke become common well before that limit is reached.
How This Calculator Works
This calculator uses two inputs: the dry-bulb (air) temperature and the relative humidity. By default, it applies the Stull (2011) formula, a well-known equation that estimates wet-bulb temperature from those two values. It works best between 0°C and 50°C.
If you open the advanced options and enter your station pressure, the calculator switches to a more precise psychrometric method. This method accounts for your local air pressure, which changes with altitude. Higher elevations have lower pressure, which affects how fast water evaporates and shifts the wet-bulb result.
The calculator also computes the dewpoint temperature using the Magnus formula. Dewpoint is the temperature at which moisture in the air starts to condense into water droplets. It helps you understand how much moisture is actually in the air. A higher dewpoint means more moisture and more discomfort. For a dedicated tool focused on dewpoint alone, see our dew point calculator.
Understanding the Heat Stress Bands
After each calculation, a color-coded band shows you the level of heat stress risk based on your wet-bulb result:
- Safe (below 23°C): Low risk for most people and activities.
- Caution (23°C–27°C): Drink water often and take breaks during hard work or exercise. Use a water intake calculator to make sure you are hydrating enough.
- Danger (28°C–30°C): Heavy activity can cause heat illness. Limit time outdoors.
- Extreme Danger (31°C–34°C): Very high risk. Reduce exposure as much as possible.
- Survival Limit Exceeded (35°C+): The body cannot cool itself. This level is life-threatening.
Who Uses Wet-Bulb Temperature?
Meteorologists use it to study humidity, fog, and cloud formation. They also pair it with the wind chill calculator during colder months to assess the full range of temperature-related risks. Military and sports organizations use it to set safe training limits. Athletes tracking performance in the heat may also benefit from tools like a heart rate zone calculator or a calories burned calculator to adjust effort for hot conditions. Factories and warehouses track it to protect workers from heat illness. Farmers use it to manage livestock and crop drying. HVAC engineers rely on it to size cooling systems, often alongside a BTU calculator to match equipment to heat loads. Anyone working or exercising in hot, humid conditions benefits from knowing the wet-bulb temperature.