the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface.
It is usually denoted Φ or ΦB. The SI unit of magnetic flux is the weber
Mathematically it is represented as B = Φ/A
where B is magnetic flux density in teslas (T),
Φ is magnetic flux in webers (Wb), and
A is area in square meters (m2).