Air Core Inductor Calculator

Air Core Inductance Calculator

This calculator computes the inductance of a coil of wire (single layer) with an air core. The output is based on the width and diameter of the coil.

Diameter (D)
Width (W)
Turns (T)
Inductance (L) µH

L = D2 x T2 / (18 D + 40 W)

Inductance is value describing how hard a device opposes a change in current. You can compare it to the inertia of a flywheel or a bicycle. It takes a push to get things moving and once they are moving they don’t want to stop. Current flowing through an inductor works the same way. Opening an electrical switch in a highly inductive circuit will cause an arc or spark because the current literally jumps through the air to keep flowing. How is this is possible? Energy storage.

Current moving through a wire inspires a magnetic field around the wire. Like a flywheel, it takes energy to get this magnetic field going. Once it is going, it doesn’t want to stop. The field is additive and by winding the wire into a cylindrical coil, the field is multiplied creating higher inductance. More turns; more inductance. The inductance can be increased further by winding the wire around iron or other materials.