Mark Perry of BuiltLean created this awesome visual chart to show images of bodies at different body fat percentages. Of course there are other factors to take into consideration like body shape, age, & fat distribution to name a few, but this gives a great basic guideline.
You can read more about it on the BuiltLean website here:
http://www.builtlean.com/2012/09/24/body-fat-percentage-men-women/