**Magnetic flux**, usually denoted by Greek letter Φ, is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. The flux through an element of area perpendicular to the direction of magnetic field is given by the product of the magnetic field density and the area element. More generally, magnetic flux is defined by a scalar product of the magnetic field density and the area element vector. The Maxwell's equations in the absence of magnetic monopoles requires that the magnetic flux through a closed surface is zero. The SI unit of magnetic flux is the weber.

*Related concepts*: gauss, henry, tesla, maxwell, oersted, weber, volt, and B-Field.

**See also**: Magnetic flux quantum