i've noticed around here that people frequently mention their body fat percentage as either part of their goal or target or as a way of monitoring their progress. this makes pretty good sense to me. what i don't understand is how you measure this? i suspect people do it at the gym, but is there a special piece of equipment or something? i don't belong to a gym.

I have an inexpensive caliper and my scale supposedly measures body fat as well. I don't really trust the scale, and am not sure I'm using the caliper right. I have read things from folks who use one regularly though, so I think it works if done right.

I think the best way is immersion in water? That has to be done at a special facility.

There are a few ways to measure body fat. Shannon is right that the most accurate way is to be totally immersed in water in a special machine that does it. Most people on 3FC who are talking about their bodyfat have probably not had this done. I don't know how much it costs but it's probably not cheap.

Then there are the calipers that are used to pinch some of your fat and measure that way. This method varies in how accurate it is. For me I don't think this would work because of my loose skin.

The most common, and most innacurate way is using a digital scale that measures body fat. I believe how it works is that the scale sends a little electrical signal through your body as you stand on it, and calculates how long (milliseconds) that it takes for this signal to travel through your body, and on this basis it is able to calculate body fat percentage. If you use this method, don't trust it 100% but it can give you a guide or a general idea, and show changes over time.