The self-inductance of a simple coil can be competed from the total magnetic energy stored in the field for a known current intensity going through the coil.

The magnetic field can be computed using one of the MagnetoStatic LF solvers (BiotSavart if possible, Vector Potential if there are metal or ferrite objects that need to be accounted for).

With these solvers, the coil has to be modeled as a filament (because only one-dimensional wires can be used as current sources). For a complete example, please follow the Tutorial "3.2.6 Self-Inductance of Qi Transmit Coil".