Inductor Series & Parallel Calculator

Combining inductors

Inductors combine just like resistors. In series the inductances add; in parallel the reciprocals add, giving a total smaller than the smallest inductor.

Series: L = L₁ + L₂ + … + Lₙ

Parallel: 1/L = 1/L₁ + 1/L₂ + … + 1/Lₙ

This assumes the inductors are not magnetically coupled — i.e. their fields don't link. If coils share a core or sit close together, mutual inductance (M) shifts the result and these formulas are only an approximation.

How it works

An inductor opposes changes in current, and that opposition is what adds up in series: current flows through each coil in turn, so their effects stack and the inductances simply sum. In parallel the current splits between branches, so each coil handles only part of it and the combined inductance drops below the smallest single value — the same reciprocal maths as resistors in parallel. Two equal inductors give double in series and half in parallel.

Worked example

A 100 µH and a 47 µH inductor give 147 µH in series. In parallel, 1/L = 1/100 + 1/47, so L ≈ 32 µH — smaller than either. If you only need a rough value in a pinch, two 100 µH coils in parallel make a handy 50 µH.

The coupling caveat, and why it matters

These formulas assume the inductors are not magnetically coupled. If two coils share a core or sit close together, their fields link and mutual inductance shifts the total up or down depending on orientation — so keep combined inductors physically separated or at right angles when you want the simple result. Series and parallel inductors let you hit a target inductance or a higher current rating from parts on hand. Designing a filter or oscillator? Pair this with theRC time constant andplanar inductor calculators.