Parallel Inductors Calculator

For inductors in parallel, use the reciprocal sum: 1/Leq = 1/L1 + 1/L2 + ... + 1/Ln, then take the reciprocal of the result. For example, 10 mH in parallel with 10 mH gives 1/(1/10 + 1/10) = 5 mH. The equivalent inductance is always smaller than the smallest inductor in the group.

Because inductive reactance XL = 2*pi*f*L scales linearly with L, exactly like resistance R does. Impedances in parallel always combine as 1/Zeq = sum(1/Zi), so inductors follow the same reciprocal rule as resistors: 1/Leq = sum(1/Li). Our parallel-resistor calculator uses the identical math with R instead of L.

Capacitive reactance Xc = 1/(2*pi*f*C) is inversely proportional to C, so capacitors combine the mirror image way: in parallel Ceq = C1 + C2 (simple sum), and in series 1/Ceq = sum(1/Ci). Inductors are the exact inverse: reciprocal sum in parallel, simple sum in series. See our parallel-capacitor calculator for the capacitor side.

Yes. For exactly two inductors, Leq = (L1 x L2) / (L1 + L2), the product over the sum. For example, 100 mH in parallel with 47 mH gives (100 x 47)/(100 + 47) = 4700/147 = 31.97 mH. This calculator shows this shortcut automatically whenever you enter two inductors.

Inductors in series simply add: Leq = L1 + L2 + ... + Ln. For example, 10 mH + 10 mH in series = 20 mH, no matter the order. If the two coils are magnetically coupled, add the mutual term: aiding (dots on the same side) gives L = L1 + L2 + 2M, opposing gives L = L1 + L2 - 2M.

Mutual inductance M measures how strongly two coils couple magnetically: M = k x sqrt(L1 x L2), where k is the coupling coefficient from 0 (no coupling) to 1 (perfect coupling). For example, k = 0.5 with L1 = L2 = 100 uH gives M = 0.5 x 100 uH = 50 uH. M can never exceed sqrt(L1 x L2), which is the k = 1 limit.

The dot marks the reference polarity of each winding. Current entering both dotted ends makes the magnetic fields aid: L = L1 + L2 + 2M. Current entering one dotted and one undotted end makes them oppose: L = L1 + L2 - 2M. Example: two 100 uH coils with M = 50 uH give 300 uH aiding and 100 uH opposing.

Yes. Every value is converted to henries before the math: 1 H = 1000 mH = 1,000,000 uH = 1,000,000,000 nH. For example, 1 H in parallel with 1000 mH and 1,000,000 uH gives Leq = 1/3 H = 333.333 mH. Mixing units never changes the result, only the display.

Current divides in inverse proportion to inductance: Ii = (Leq / Li) x Itotal, so the smallest inductor carries the most current. For 10 mH in parallel with 10 mH and 2 A total, each branch carries exactly 1 A. Warning: a zero-inductance branch is an ideal short and takes all the current.

Stored energy is E = 1/2 x L x I^2; for example 5 mH at 2 A stores 0.5 x 0.005 x 4 = 0.01 J (10 mJ). Inductive reactance is XL = 2 x pi x f x L; for example 100 mH at 50 Hz gives XL = 31.42 ohms, so 1 A RMS drops 31.42 V RMS across the coil. This calculator computes E, XL, angular frequency, and coil voltage together. For a dedicated 3-way XL/f/L solver see our Inductive Reactance Calculator, and for a dedicated E/L/I energy solver see our Inductor Energy Calculator.