There is a new extended and updated wetsuit size guide artice on 360guide.info, I suggest you you read that one.
If you never wore a wetsuit and you are wondering how to choose the right size wetsuit for you then read this. BTW – first you should read our little How to put on your wetsuit post.
Choosing Wetsuit Size
Wetsuit should feel snug and tight all over, but it should not force you to bend over. If it does, than the body part of the wetsuit is to small and you should get a size bigger wetsuit or maybe a tall version of the same size. Tall version? Yes, many times there is a T for TALL model of the small and especially medium size wetsuits. Like MS, M and MT. This means that if you are skinny and tall you should maybe get a medium tall wetsuit and not a Large one because large wetsuit will be loose and you will be constantly flushed with cold water.
After the wetsuit is installed on your body :) try crouching, bending over, jumping, moving your arms (and sweating up the wetsuit) to see if there are any restrictions of movement and if the sleeves are long enough.
A good test for the size of the wetsuit is this: pull the neoprene on your back just above your backside away from our body. There should not be to big of a gap between your body and the wetsuit. Because of the curve of your back this is the first place where you can see if the wetsuit is to big. Then again, we are all built different so it is hard to find a perfect fit. New more elastic neoprene makes choosing the right wetsuit size much easier.