If I have a simple bar magnet which is say 'w' x 'h' metres in dimension placed on a plane, say at cartesian coordinates (xM, yM), how can I work out the magnetic field strength at some arbitary point (x, y) also on that plane. I've searched the internet but can only find equations to do with electomagnets or magnetism due to electic current. Nothing for a plane old chunk of iron. I just need the equations, you can define the properties of the magnet such as how strong it is. Thanks.