Both of them can be easily calculated for a solenoid magnet, but if the magnet is toroidal shaped, it is practically impossible to calculate the magnetic energy analytically.

Image: US ITER. The central solenoid is 4.13 m across (that’s 13′ 7″ for burger enthusiasts) sits at the hole of the “doughnut” of the toroidal reactor.

Both of them can be easily calculated for a solenoid magnet, but if the magnet is toroidal shaped, it is practically impossible to calculate the magnetic energy analytically.