This came up in a GBSB 2021 video hosted by Madalynne of Madalynne Intimates. She was talking about body suit length, and how to adjust it. There was something she said that I found interesting, and wanted to make a note of it.

What the torso is

The torso is the main part of the body, from the base of the neck down to where the legs attach. When using pre-made patterns, it is helpful to know your general torso length ahead of time, so you can have a general idea how the pattern will fit. This can be useful in several other garments as well, including swimsuits and underwear.

How to determine torso length

To determine this, put your elbow next to your body. If your elbow point is below your waist, you have a short torso. Alternatively, if your elbow point is above your waist, you have a long torso. If your elbow point and torso are even, you have a balanced torso.

The logic behind it

I never thought about this before, but it does make sense now that I think about it. Since your wingspan is related to your height, it would mean longer arms means more height. The relationship of your waist and your elbow will give an idea about how much or your height is legs and how much is torso.