[Reach]

I'm not fat, but I have no idea how much body fat I have. How do you even figure that out?

Calipers are the most reliable. You can buy them at many drug or fitness stores.

Alternatively, many scales use bioelectrical impedance analysis to estimate body fat, but it tends to overestimate it since it can't differentiate between fat and water.


As for building muscle...it's complicated. The short answer is go to the gym, lift heavy weights, do compound movements and eat tons of food so you gain weight.

The long answer? Well, that will depend on what you need to know, haha.