Force on a current in magnetic field F = BIL sin (theta) where the units of B are T, tesla.

The flux density of a field of one tesla is therefore defined as the force per unit length on a wire carrying a current of one ampere at right angles to the field.

Fleming's left hand rule for motor from
Magnetic flux (φ) = Magnetic flux density (B) x Area (A)
The magnetic flux passing through a surface as BA where A is the area of the surface at right angles to the field. Magnetic flux (φ) is measured in webers (Wb).