Magnetic Flux Calculator
Enter a magnetic field strength and an area to get the magnetic flux in webers — the total amount of field passing through a surface held perpendicular to it.
Flux in one step
Enter the field strength in tesla and the area in square metres and the calculator returns the magnetic flux (Φ = B × A) in webers instantly.
Use SI units
Field strength in tesla (T) and area in square metres (m²) give flux in webers (Wb). One weber equals one tesla times one square metre.
What is magnetic flux?
The field passing through a surface
This magnetic flux calculator measures how much magnetic field passes through a given surface. Magnetic flux is the product of the magnetic field strength and the area it threads through, and it captures the total "amount" of field crossing that surface. When the field is perpendicular to a flat area, the flux is simply the field strength multiplied by the area. It is the quantity behind transformers, electric generators, and induction: a changing flux through a coil is what induces a voltage, which is the heart of how most electrical power is produced and converted.
Enter a field strength in tesla and an area in square metres to get the magnetic flux in webers instantly.
For a uniform field perpendicular to a flat surface, the magnetic flux is the field strength multiplied by the area.
Φ = B × AHere Φ is the magnetic flux in webers, B is the magnetic field strength (also called magnetic flux density) in tesla, and A is the area in square metres. Suppose a uniform 0.5 T field passes straight through a flat loop of area 0.2 m². Multiplying the two gives Φ = 0.5 × 0.2 = 0.1 Wb. Because flux is a direct product, doubling either the field or the area doubles the flux — there is no squaring or other non-linear term to worry about.
The formula is exact, but a couple of practical points are worth keeping in mind.
Perpendicular field and consistent units
This calculator assumes the magnetic field is uniform and perpendicular to the area. If the field meets the surface at an angle θ from the normal, the flux is reduced to Φ = B × A × cos θ — set θ to zero (cos θ = 1) for a perpendicular field, which is what this calculator computes. Keep your units consistent — tesla for the field and square metres for the area — so the result comes out in webers.