Wet Bulb Calculator

The Wet Bulb Calculator determines wet bulb temperature from dry bulb temperature and relative humidity. Wet bulb temperature is crucial for HVAC design, cooling tower performance, evaporative cooling systems, and human comfort assessment in hot climates.

Modify the values and click the calculate button to use
Dry Bulb Temperature °C
Relative Humidity %
Temperature Unit  
Atmospheric Pressure kPa

Related Relative Humidity Calculator | Dew Point Calculator | Psychrometric Calculator

Understanding Wet Bulb Temperature

Wet bulb temperature is the lowest temperature that can be reached by evaporative cooling. It represents the temperature of a wet thermometer bulb exposed to moving air, where evaporation cools the bulb until equilibrium is reached between heat and mass transfer.

Key Concepts

Physical Meaning

Wet bulb temperature indicates:

Relationship to Other Parameters

Calculation Methods

Iterative Psychrometric Method

The most accurate method involves iterative solution of psychrometric equations:

  1. Assume initial wet bulb temperature
  2. Calculate saturation vapor pressure at wet bulb temperature
  3. Apply psychrometric constant and energy balance
  4. Iterate until convergence

Approximation Formula (Stull 2011)

For quick estimates at standard pressure:

Tw = T × atan[0.151977 × (RH% + 8.313659)^0.5] + atan(T + RH%) - atan(RH% - 1.676331) + 0.00391838 × (RH%)^1.5 × atan(0.023101 × RH%) - 4.686035

Applications

HVAC and Cooling Systems

Industrial Processes

Human Comfort and Safety

Wet Bulb Globe Temperature (WBGT)

Related to wet bulb temperature, WBGT is used for heat stress assessment:

Critical Wet Bulb Temperatures

Wet Bulb (°C) Wet Bulb (°F) Condition Impact
< 15 < 59 Comfortable No heat stress concerns
15-20 59-68 Caution Monitor activity levels
20-25 68-77 Warning Limit strenuous activity
25-30 77-86 Danger Heat exhaustion likely
> 30 > 86 Extreme Danger Heat stroke imminent

Measurement Techniques

Sling Psychrometer

Aspirated Psychrometer

Electronic Instruments

Factors Affecting Accuracy

Measurement Conditions

Environmental Factors

Design Applications

Evaporative Cooling Systems

Natural Ventilation

Note: Wet bulb temperature calculations are most accurate when using iterative psychrometric methods. Simple approximations may have errors of ±1-2°C under extreme conditions.