Mass-Energy equivalence

% units
2084 units, 71 prefixes, 32 nonlinear units

You have: g c^2
You want: kiloton tnt
        * 21.480764
        / 0.046553278

You have: gigaton tnt
You want: lb c^2
        * 102.63241
        / 0.0097435108 

So, one gram is equivalent to 21 kiloton TNT (about the Nagasaki atomic bomb), and small 100 pound person is a 1000 megaton nuclear weapon, far larger than has ever been constructed.