# How to calculate wet bulb globe temperature (WBGT) using only temperature and humidity?

Greetings fellow scholars,

I'm trying to answer the question above because I've come across WBGT calculators like this one (https://www.climatechip.org/heat-stress-index-calculation) and I don't understand how the answers are derived using the Liljegren method without more variables (other than temperature, humidity and assumptions on direct sunlight and wind speed).

The paper, Liljegren et al. (2008), method is pay walled. I've tried digging into the code of projects like this one but they're using more variables.

If anyone can give an explanation of what's going on with these calculators or point me to a code repo/paper where I can try learn more, please do.

Explicit Calculations of Wet-Bulb Globe Temperature Compared With Approximations and Why It Matters for Labor Productivity might help explain what's going on.

Liljegren's method appears to be calculation intense. It involves three equations, the two main ones are for Tw & Tg, equations 3 & 5. The equations needs to be solved by iteration.

$$..............(3)$$

$$..............(4)$$

$$..............(5)$$

By ignoring direct sunlight & wind speed, the web page you link to is simplifying things & producing an approximation; something similar to calculating sW BGT, equation 1.

$$.............(1)$$