There's a few ways to find body fat percentage. You can use a caliper, use the water or air displacement methods (expensive). For not so accurate, but cheaper methods, there's just finding a list of pictures of people at difference body fat %s and comparing, biometric impedance scales, you can find you BMI (I dislike this because it just compares height and weight, which ignores fat/muscle ratios), you can take your measurements and do the math.
Best methods would be the fat caliper or the look and compare methods.
Powerline!Max - A Goofy Movie (Otakon 2015, completed)
Possible Future Cosplays
Ippo (Hajime no Ippo)
Teen Goku (Dragonball/ Dragonball Z)
Steve Rogers civilian uniform (Captain America: First Avenger)
Rupert: humanoid version (Family Guy, probably won't happen)
My Facebook cosplay group - Southern Maryland Cosplay
(Anyone can join)
Author of the "Getting Fit for Cosplay" Katsucon panel.