This question is out of curiosity. I'm not making anything with magnets, it just called my attention after spending hours clicking link after link in Wikipedia and reading stuff after stuff. I don't even remember how I got here anymore, I was reading electrostatic forces between organic molecules, but everything was connected one way or the other. Anyway, this equation, it says for Bar magnets. As far as I'm concerned, a bar magnet is not circular or has any geometrical similarities with circles or spheres. It's rectangular. Then, why does it has an R for radius. Isn't "radius" supposed to be a geometrical exclusive property of circles, spheres and other geometric figures containing one of those two? I honestly think there must be something wrong with it.