Work out inductors in series instantly with clear inputs, formula shown and shareable results.
Inductors in series add, but if their fields interact the mutual inductance adds twice: Ltotal = L1 + L2 + 2M with M = k x sqrt(L1 x L2). The sign depends on winding orientation, so aiding fields increase inductance and opposing fields reduce it.
Series inductance
Ltotal = L1 + L2 + 2M, M = k sqrt(L1 L2); k = 0 for uncoupled coils
Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.
When the coils are far apart, at right angles, or shielded. Toroids couple very little because their flux is contained.
Then M is subtracted twice, and with perfect coupling of equal coils the total inductance falls to zero — the principle behind a non-inductive winding.