${\displaystyle H=\frac{B}{{\mu }_0}-M}$

NOTE 1 – In vacuum, the magnetic field strength is at all points equal to the magnetic flux density divided by the magnetic constant:

${\displaystyle H=\frac{B}{{\mu }_0}}$

NOTE 2 – The rotation of the magnetic field strength is the total current density J_t:

rot H = J_t

NOTE 3 – The magnetic flux density B is sometimes called “magnetic field”, risking confusion with the magnetic field strength H.