In the International System of Quantities used with the SI, there are two conventions for defining magnetic charge q m, each with different units: weber (Wb) and ampere -meter (A⋅m). The conversion between them is q m = μ 0 q m, since the units are 1 Wb = 1 H⋅A = (1 H⋅m)(1 A⋅m), where H is the henry – the SI unit of inductance.