What is the SI unit of magnetic flux?

The SI unit of magnetic flux is the weber, symbol Wb.

Magnetic flux measures the amount of magnetic field passing through a surface. For a uniform field, it can be calculated as the magnetic flux density multiplied by area and the appropriate angle factor. One weber is equal to one tesla-square metre, or one volt-second: 1 Wb = 1 T·m² = 1 V·s.

The unit is named after Wilhelm Eduard Weber, a German physicist who made important contributions to electromagnetism and worked with Carl Friedrich Gauss. The weber is an SI derived unit, expressed in base units as kg·m²·s⁻²·A⁻¹.

A frequent confusion is between magnetic flux and magnetic flux density. Flux is measured in webers, while flux density is measured in teslas. Another distractor, the maxwell, is the CGS unit of magnetic flux; one maxwell equals 10⁻⁸ weber. The henry measures inductance, and the tesla measures field strength per unit area rather than total flux.

Faraday’s law connects flux to induction: a changing flux through a circuit produces an electromotive force.