# Wet-Bulb Temperature Calculator

URL: https://speedycalculator.com/calculators/physics/wet-bulb/
Last updated: 2026-10-30

> The wet-bulb temperature calculator estimates the wet-bulb temperature from the air temperature and relative humidity using Stull's 2011 formula, and indicates the heat-stress risk.

## Inputs

- Air temperature (°C, °F, K)
- Relative humidity (%)

## Results

- Wet-bulb temperature
- Wet-bulb depression

## Formula

```
T_w = T·atan(0.151977·(RH + 8.313659)^{1/2}) + atan(T + RH) − atan(RH − 1.676331) + 0.00391838·RH^{3/2}·atan(0.023101·RH) − 4.686035
```

## Explanation

The wet-bulb temperature is the lowest temperature evaporation can cool something to. The human body relies on sweat evaporation, so a wet-bulb temperature of 35 °C is thought to be the limit of human survival even in shade.

### How to use the Wet-Bulb Temperature Calculator

- **Air temperature**
- **Relative humidity (%)**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Enter the air temperature and relative humidity (valid for 5–99% RH and −20 to 50 °C at sea-level pressure).

### Inputs explained

FieldWhat to enterAir temperatureUnits: °C, °F, KRelative humidity (%)A number

### Example values

How the main result changes when **Air temperature** changes and everything else stays at the example values above:

Air temperature (°C)Wet-bulb temperature (°C)159.400422.515.84883022.296837.528.74474535.1924

## Worked example

Inputs — Air temperature: 30 °C; Relative humidity (%): 50.

Results — **Wet-bulb temperature = 22.2968 °C**; Wet-bulb depression = 7.7032 °C.

## Key terms

- **Wet-bulb depression**: Difference between dry- and wet-bulb temperature.

## FAQ

**What is wet-bulb temperature used for?**
Heat stress, evaporative cooling, cooling towers and snowmaking.

**How accurate is Stull's formula?**
Mean absolute error under 0.3 °C in its valid range; individual errors range from about −1 to +0.65 °C.

**Why is 35 °C wet-bulb deadly?**
The body can no longer shed heat by sweating.

**Is it the same as WBGT?**
No – WBGT also includes radiation and wind.


## Sources

- [NOAA / National Weather Service – Weather calculators](https://www.weather.gov/epz/wxcalc)
- [Vaisala – Humidity conversion formulas](https://www.vaisala.com/en/lp/humidity-conversion-formulas)
- [Stull (2011), Wet-bulb temperature from relative humidity and air temperature, J. Appl. Meteor. Climatol.](https://doi.org/10.1175/JAMC-D-11-0143.1)