Self-inductance calculations are presented for coils of modular construction. Individual modules have a fixed winding density, so that a complete multi-module coil will be characterized by larger inter-turn spacing at its extremities to provide suitable insulation strength under impulse voltage conditions. Gives inductance computations using finite-element analysis, so that empirical correction factors to take account of end-effects and inter-turn spacing are unnecessary. Comparison where possible with established empirical methods shows consistency. Gives an example of oscillatory high-voltage tests.