Proton Radius
(3.7037037037037e-28 m / 6.66666666666e-11) * ((3 * 4)^2) = 8e-16 m
Pi = 3
(2 * G * (0.25 kg)) / (c^2) = 3.71295774e-28 m
((3.71295774e-28 m) / G) * ((4 * pi)^2) = 8.7851327e-16 m
Exact .....
http://physics.nist.gov/cgi-bin/cuu/Value?rp
0.8751e-15 m
Black Hole proton
(((8 * pi^2 * 8.7851327e-16^3 m)) / (5.39116e-44 s) = 0.99301 m/s