Magnetic Flux Calculator
Use this tool to calculate magnetic flux through a surface and total flux linkage through a coil.
What this flux calculator does
Magnetic flux tells you how much magnetic field passes through a given area. This calculator is designed for students, engineers, and curious learners who want a quick, reliable way to evaluate flux in practical setups like coils, loops, sensors, and lab experiments.
Enter magnetic field strength, exposed area, and orientation angle, then the tool computes the signed flux in webers (Wb). It also calculates flux linkage when multiple turns are involved.
The core equation behind magnetic flux
Magnetic flux formula
Φ = B × A × cos(θ)
- Φ = magnetic flux (Wb)
- B = magnetic flux density (tesla, T)
- A = area (m²)
- θ = angle between magnetic field and the normal to the surface
If you have a coil with multiple turns, total flux linkage is:
λ = N × Φ
where N is the number of turns and λ is in weber-turns.
How to use the calculator correctly
Step-by-step
- Enter B in tesla.
- Enter A in square meters.
- Enter θ as the angle with the surface normal (not always the surface plane).
- Add turns N if you want flux linkage.
- Click Calculate Flux.
A positive result means the field aligns with your chosen normal direction. A negative value means opposite direction. The magnitude still indicates the amount of flux passing through.
Quick examples
Example 1: Surface directly facing the field
Let B = 0.4 T, A = 0.05 m², and θ = 0°. Since cos(0°) = 1: Φ = 0.4 × 0.05 = 0.02 Wb.
Example 2: Tilted surface
Let B = 0.4 T, A = 0.05 m², and θ = 60°. Since cos(60°) = 0.5: Φ = 0.4 × 0.05 × 0.5 = 0.01 Wb.
Example 3: Coil linkage
If Φ = 0.01 Wb and N = 250 turns, then: λ = 250 × 0.01 = 2.5 Wb-turns.
Common mistakes to avoid
- Using the angle relative to the surface instead of the normal.
- Mixing units (for example, cm² entered as m²).
- Forgetting the sign of flux when direction matters.
- Assuming flux and flux density are the same quantity.
Why flux matters in real systems
Magnetic flux is central to transformers, generators, motors, inductors, magnetic sensors, and many control systems. Any time field lines cross a loop or core, flux is the quantity that links geometry and field strength.
It is also the starting point for Faraday's Law: changing flux linkage induces voltage. In other words, understanding flux is a key step toward understanding electromagnetic energy conversion.
Final takeaway
A good flux calculator saves time and reduces mistakes. Keep your units consistent, use the correct angle definition, and check whether the sign of the result matters for your application. With those habits, you can move from formula to correct answer quickly and confidently.