# Wet Bulb Temperature Calculator

> Wet bulb temperature calculator: compute wet bulb from air temperature, humidity and pressure, with heat stress risk levels. Free, runs in your browser.

- **Canonical URL:** https://boringtoolskit.com/wet-bulb-temperature-calculator/
- **Category:** Geography
- **Evidence level:** authored-methodology
- **Reviewed:** July 26, 2026
- **Last verified:** 2026-10-12
- **Privacy:** Inputs and results stay in this browser unless the page clearly labels an external request.

## How it works

Stull approximation: Tw = T x atan(0.151977 x (rh + 8.313659)^0.5) + atan(T + rh) - atan(rh - 1.676331) + 0.00391838 x rh^1.5 x atan(0.023101 x rh) - 4.686035, T in Celsius, rh in %.

## Worked example

At 32 C and 60% relative humidity, the wet-bulb temperature is about 25.8 C (78.4 F), which falls in the caution zone for outdoor exertion.

## Assumptions

- Valid for 5 to 99% RH and roughly -20 to 50 C air temperature (Stull 2011).
- Wet-bulb approximates the lowest temperature reachable by evaporative cooling.

## Common questions

### What wet-bulb temperature is dangerous?

Sustained wet-bulb above about 25 C signals serious heat stress; near 35 C is survivable for only hours.

### Why is wet-bulb worse than regular temperature?

It measures evaporative cooling limits: humid air blocks sweat from cooling you.

## Related tools

- /heat-index-calculator/
- /dew-point-calculator/
- /wind-chill-calculator/

## Sources

- [Heat safety and wet-bulb guidance](https://www.weather.gov/safety/heat)
- [Calculation methodology](/methodology/)

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