${\Phi }_{\mathrm{C}}=\Phi +{\mu }_0{\lambda }^2{\displaystyle \underset{\text{C}}{\int }𝑱\cdot \text{d}𝒍}$

where $\Phi$ is the magnetic flux in the area, $\lambda$ is the London penetration depth, $𝑱$ is the superconducting current density, ${\mu }_0$ is the magnetic constant and $\text{d}𝒍$ is a vector line element

Note 1 to entry: The fluxoid in a superconductor is quantized to a multiple of the flux quantum ${\Phi }_0$.

Note 2 to entry: The fluxoid is sometimes used instead of the fluxon, which exists far from the surface of a superconductor.

Note 3 to entry: This entry was numbered 815-10-15 in IEC 60050-815:2015.