Case 1
- Magnetic field strength
- 0.5T
- Area the field passes through
- 0.2m²
0.100000Wb
Open with these valuesMagnetic Flux Calculator
0.100000Wb
Result: 0.100000 WbMagnetic flux is the field strength times the area it threads through: 0.5 T across 0.2 m² carries 0.1 Wb. The field is taken as perpendicular to the surface; at an angle θ from the normal, multiply by cos θ. A negative field simply reverses the sign of the flux.
The numbers at a glance
Held fixed: Magnetic field strength 0.5000 T.
| Area the field passes through (m²) | Result (Wb) |
|---|---|
| 0.050000 | 0.025000 |
| 0.100000 | 0.050000 |
| 0.150000 | 0.075000 |
| 0.200000Your value | 0.100000 |
| 0.250000 | 0.125000 |
| 0.300000 | 0.150000 |
| 0.350000 | 0.175000 |
| 0.400000 | 0.200000 |
Worked examples
Case 2
- Magnetic field strength
- 1.2T
- Area the field passes through
- 0.25m²
0.300000Wb
Open with these valuesCase 3
- Magnetic field strength
- 0.0001T
- Area the field passes through
- 100m²
0.010000Wb
Open with these valuesHow it's calculated
Φ = B × A
- StepEnter the flux density B in tesla — a fridge magnet is around 0.5 T.
- StepEnter the area the field passes through, in square metres.
- ResultRead the flux in webers; one weber is one tesla-square-metre.
Reference table
| Field, area | Where you meet it | Flux (Wb) |
|---|---|---|
| 0.05, 0.002 | Weak field, small coil | 0.0001 |
| 0.0001, 100 | Earth-scale field over a 100 m² loop | 0.01 |
| 0.5, 0.2 | Fridge magnet across a hand-sized loop | 0.1 |
| -0.5, 0.2 | Same loop, field pointing the other way | -0.1 |
| 2.5, 0.04 | Strong magnet, small pole face | 0.1 |
| 1.2, 0.25 | Motor air gap | 0.3 |
| 1, 1 | One tesla through one square metre | 1 |
Questions
How do I calculate magnetic flux?
Multiply the magnetic field strength by the area it passes through: Φ = B × A. Use tesla for the field and square metres for the area to get the flux in webers. A 0.5 T field through a 0.2 m² loop gives 0.1 Wb.
What is magnetic flux?
Magnetic flux is a measure of the total magnetic field passing through a surface. It combines how strong the field is with how large an area it threads through. It is measured in webers, where one weber equals one tesla times one square metre.
What is the difference between magnetic flux and flux density?
Magnetic flux density is the field strength B in tesla — it describes how concentrated the field is at a point. Magnetic flux Φ is that density multiplied by the area it passes through, measured in webers, and describes the total field over a whole surface.
What if the field is not perpendicular to the area?
When the field meets the surface at an angle θ measured from the normal, only the perpendicular component counts, so the flux becomes Φ = B × A × cos θ. This calculator assumes a perpendicular field, where cos θ is 1 and the flux is simply B × A.
Why does magnetic flux matter?
A changing magnetic flux through a coil induces a voltage — Faraday's law of induction, the principle behind generators, transformers and inductors. Calculating the flux is the first step in working out the voltage an alternating field can produce.
Sources and last check
Information, not professional advice.