Of all things I'm concerned, this one should be the most confusing ever. I'll tell how... E=mc2 That is, energy is an object's mass times the speed of light squared. Mass is w*g, and g is 9.81 for so long you're on Earth. Then, the speed of light is 299,792,458 m/s*299,792,458 m/s, which is 8.98755179*1016 m2/s2 (okay, this part is where I get confused. How much is 8.98755179*1016 m2/s2 then?) So; E=(wg)*(8.98755179*1016 m2/s2) My second doubt is here. If wg would give a result in Newtons, then in what unit will the result would be if E=mc2? Please give me an example. I'll give the values. The mass should be 335.564 N. Please show me how you calculate the rest. Thanks.