This formula is valid only for a solenoidal current sheet. Weaver’s article Numerical Methods for Inductance Calculation is used for calculations of inductance L S:
A single-layer inductor is shown in the picture above: D c is the coil diameter, D is the coil former diameter, l is the coil length, p is the coil pitch, d is the wire without insulation diameter and d i is the wire with insulation diameter.