Solenoid Inductance

How to use this calculator

Pick the core cross-section shape — Round (enter the diameter) or Square (enter the side) — then set the coil length, the number of turns and the core's relative permeability µr (1 for air). The calculator uses L = µ₀·µr·N²·A / l, where µ₀ = 4π×10⁻⁷ H/m and A is the core cross-sectional area, and returns the inductance in H/mH/µH. Every change recomputes instantly.

What the value means in a circuit

A solenoid concentrates magnetic flux along its axis; the inductance scales with the square of the turn count (doubling N gives 4× L), with the core area, and with a high-µr core (ferrite or iron). This is the basis of electromagnets, relays, RF chokes, transformers and the energy-storage inductor in a switching power supply. The formula assumes the coil is long compared to its core dimension; for very short coils a geometry correction factor is needed, so treat short-coil results as an approximation.