Wet Bulb Temperature Calculator

The wet-bulb temperature is the lowest temperature evaporation can cool something to. It combines heat and humidity and is a key measure of heat stress.

How to use the Wet Bulb Temperature Calculator

Enter the air (dry-bulb) temperature.
Enter the relative humidity.
Read the wet-bulb temperature and heat stress level.

How it works

A wet-bulb thermometer has its bulb wrapped in a wet cloth; evaporation cools it below the air temperature unless the air is saturated. This calculator uses Roland Stull’s 2011 empirical formula, which estimates wet-bulb temperature from air temperature and humidity at sea-level pressure, accurate to about ±1 °C for 5–99% humidity and −20 °C to 50 °C.

Sweat cools the body only if the skin is warmer than the wet-bulb temperature, so high wet-bulb readings make heat dangerous even for healthy people in the shade.