You can use calipers which gauge certain points on your body.
You can use a handheld device which shoots a current through your body and tells you.
You can do it in water with some sort of device
You can do it in an egg-shaped chamber (did this for college...was weird)
Personally I just gauge myself in the mirror.
<10% is pretty ripped
11-15% is in really good shape but you have about 5-15 lbs of fat to lose before you expose all your abs
16%+ is you need to get to work...
That's just my own personal scale I use.



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