Wet Bulb Temperature Calculator

Author: Henrick Yau
- 1 October 2026
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Calculators

Calculate wet bulb temperature, heat index, and humidity parameters for meteorology, HVAC design, and heat stress assessment. Essential for understanding thermal comfort and safety conditions.

Environmental Conditions

Ambient air temperature
%
Percentage of moisture saturation
Barometric pressure at location
Height above sea level

Calculation Method

Choose calculation accuracy vs speed
Air movement speed (affects cooling)

Display Options

Understanding Wet Bulb Temperature

Wet bulb temperature is the lowest temperature that can be reached by evaporative cooling. It represents the temperature a thermometer would read if wrapped in a water-soaked cloth with air blowing over it.

Key Concepts
  • Dry Bulb Temperature: The ambient air temperature measured by a regular thermometer
  • Wet Bulb Temperature: Temperature accounting for humidity and evaporative cooling
  • Relative Humidity: Percentage of water vapor in air compared to saturation point
  • Dew Point: Temperature at which air becomes saturated with water vapor
  • Heat Index: How hot it feels when humidity is factored with actual temperature
Calculation Methods
  • Stull Formula: Simple empirical formula for quick estimates
  • Bolton Formula: More accurate meteorological standard
  • Iterative Method: Highest precision using thermodynamic principles
  • Quick Approximation: Fastest calculation for rough estimates
Applications
  • Meteorology: Weather forecasting and climate analysis
  • HVAC Design: Cooling system sizing and efficiency
  • Industrial Safety: Heat stress prevention in workplaces
  • Agriculture: Crop stress and irrigation planning
  • Sports Medicine: Athlete safety in hot conditions
  • Building Design: Natural ventilation and cooling strategies
Heat Stress Guidelines
  • 35°C (95°F) Wet Bulb: Dangerous - Maximum survivable limit
  • 32°C (90°F) Wet Bulb: Very High Risk - Limit outdoor activities
  • 28°C (82°F) Wet Bulb: High Risk - Exercise caution
  • 24°C (75°F) Wet Bulb: Moderate Risk - Monitor vulnerable populations
  • Below 21°C (70°F): Low Risk - Generally safe conditions
Factors Affecting Wet Bulb Temperature
  • Air Temperature: Higher temperatures increase wet bulb temperature
  • Humidity: Higher humidity brings wet bulb closer to dry bulb temperature
  • Atmospheric Pressure: Affects evaporation rate and calculation accuracy
  • Wind Speed: Increases evaporation rate, affecting apparent temperature
  • Altitude: Lower pressure at elevation affects psychrometric properties

Disclaimer: This calculator provides estimates based on established psychrometric formulas. For critical applications involving human safety, industrial processes, or medical conditions, consult qualified professionals and use calibrated instruments. Results should not be used as the sole basis for safety decisions in extreme heat conditions.

What Wet Bulb Temperature Measures

The Wet Bulb Temperature Calculator is a handy tool for gauging thermal comfort and environmental heat stress. It takes standard meteorological data—such as air temperature, humidity, and pressure—to approximate the "wet bulb" temperature. This figure is crucial for understanding how the body copes with heat, particularly when sweat evaporation becomes less efficient.

Widely employed in weather monitoring, HVAC design, sports safety, and workplace heat stress assessments, this calculator aids in making well-informed decisions regarding comfort, health, and performance.

Stull Formula for Wet Bulb Temperature

Stull Formula (for estimating wet bulb temperature):
\( T_{wb} = T \cdot \arctan(0.151977 \sqrt{RH + 8.313659}) + \arctan(T + RH) - \arctan(RH - 1.676331) + 0.00391838 (RH)^{1.5} \cdot \arctan(0.023101 \cdot RH) - 4.686035 \)

Enter Temperature, Humidity, and Pressure

Follow these straightforward steps to obtain precise readings:

  • Key in the Dry Bulb Temperature—the air temperature as measured by a standard thermometer.
  • Provide the Relative Humidity as a percentage (0-100%).
  • Set the Atmospheric Pressure using your preferred unit of measurement.
  • For more comprehensive calculations, you may add Altitude and Wind Speed.
  • Select a Calculation Method—from quick estimates to highly accurate iterative approaches.
  • Hit "Calculate Wet Bulb Temperature" to view your results.

Why Wet Bulb Temperature Matters

This metric indicates the lowest temperature achievable through evaporative cooling. It's more than just a figure—it's a direct reflection of how effectively the body can cool itself under varying conditions. As wet bulb temperatures climb, sweat evaporation slows, heightening the risk of overheating.

Using this calculator offers insights akin to employing a carbon footprint tool—both help uncover hidden factors influencing comfort and safety. Just as tools like a car CO₂ tracker or a flight emissions tool quantify impact, this calculator reveals the unseen burden of heat and humidity on the body.

Practical Benefits

  • Heat Stress Monitoring: Identify when conditions turn hazardous for outdoor work or sports.
  • HVAC Efficiency: Optimise cooling systems for energy savings and enhanced comfort.
  • Personal Awareness: Spot risk periods and schedule breaks, hydration, and shade accordingly.
  • Thermal Comfort Planning: Design better indoor and outdoor spaces.

Questions About Wet Bulb Temperature

Q: What is the difference between dry bulb and wet bulb temperature?

A dry bulb measures the ambient air temperature. A wet bulb factors in humidity and evaporation, indicating how cool the air feels once sweat evaporates.

Q: Why should I be concerned about wet bulb temperature?

It's a critical factor in thermal safety. When the wet bulb reading is excessively high, the body struggles to cool down, even with perspiration.

Q: What’s the best method to use?

For everyday purposes, the “Stull” method provides quick and reasonably accurate results. For critical scenarios, like industrial safety, opt for the “Iterative” method to achieve high precision.

Q: Is this similar to a carbon calculator?

In some ways, yes. Just as a personal carbon tracker shows your environmental impact, this tool illustrates the thermal strain on your body. Both assist in making safer, more informed choices.

Who benefits from wet bulb temperature readings?

  • Families planning outdoor activities can determine safe times for play.
  • Employers and site supervisors can evaluate heat stress risks at work sites.
  • Engineers and architects can incorporate better ventilation solutions.
  • Athletes and coaches can schedule training to prevent heat-related issues.

Complementary Tools

If you're keen on environmental health and sustainability, this tool pairs well with:

  • Household emissions guides for tracking energy use and comfort needs
  • Flight CO₂ estimators to compare heat stress across different locations
  • Public transport emissions calculators to assess daily travel comfort in warmer months
  • Solar energy output calculators to explore cooling potential from solar-powered fans and air conditioners

Plan for Heat Safety With This Calculator

The Wet Bulb Temperature Calculator empowers you to manage your environment—whether for comfort, safety, or sustainability. Use it just as you would a mileage estimator or a fuel usage tracker: to plan ahead, optimise, and stay safe.