Wet Bulb Calculator
Estimate Tw from T and RH
How to Use This Calculator
1
Enter Dry-bulb Temperature
Ambient air temperature in °C.
2
Enter Relative Humidity
Percentage between 0 and 100.
3
Calculate
Result shows approximate wet-bulb temperature.
Formula
Tw ≈ T·atan(0.151977·√(RH+8.313659)) + atan(T+RH) − atan(RH−1.676331) + 0.00391838·RH^1.5·atan(0.023101·RH) − 4.686035
Valid approx for −20°C ≤ T ≤ 50°C, 5% ≤ RH ≤ 99%
Note: For engineering accuracy, psychrometric iterations are recommended.
About Wet-bulb Temperature
Wet-bulb temperature reflects the lowest temperature achievable by evaporative cooling at constant pressure. It is critical in HVAC and heat-stress safety.
Frequently Asked Questions
Is this exact?
This uses Stull's empirical approximation; it is close over common ranges.
Why does Tw matter?
It indicates evaporative cooling potential and human heat stress thresholds.