Inductor Parallel Value Calculator

Parallel inductors reduce the inductance seen by the circuit. The calculator produces the Equivalent inductance for two required inductor branches and, when used, a third parallel branch. That value is used when checking the effective inductance of a filter, choke network, or power-electronics circuit after individual inductors are connected across the same two circuit nodes.

The calculated equivalent inductance is lower than any participating individual inductance under the ideal uncoupled-inductor condition. It is an electrical design value—not a conductor ampacity, AWG, kcmil, raceway fill, branch-circuit, feeder, or voltage-drop result.

Parallel Inductance Inputs

Enter all inductance values in the same unit shown by the calculator: mH.

Field	Entry requirement	Electrical meaning
Inductance 1	Required; positive value	Inductance of the first parallel branch
Inductance 2	Required; positive value	Inductance of the second parallel branch
Inductance 3 (optional)	Enter a positive value to include it; enter 0 to omit it	Inductance of an optional third parallel branch

The calculator reports:

Result	Meaning
Equivalent inductance	The ideal inductance of one replacement inductor producing the same parallel inductance behavior
Participating inductors	The count of entered inductors included in the calculation

The two required fields establish the minimum parallel network. Inductance 3 (optional) is not treated as a zero-inductance branch when its value is 0; the calculator omits it and counts only the two participating inductors.

Equivalent Inductance Formula

For ideal inductors connected in parallel with no magnetic coupling, add the reciprocals of the participating inductances and then take the reciprocal:

\(\displaystyle \frac{1}{L_\text{eq}}= \frac{1}{L_1}+ \frac{1}{L_2}+ \frac{1}{L_3}\)

\(\displaystyle L_\text{eq}= \frac{1}{ \left(\frac{1}{L_1}\right)+ \left(\frac{1}{L_2}\right)+ \left(\frac{1}{L_3}\right)}\)

When Inductance 3 (optional) is entered as 0, it is omitted:

\(\displaystyle L_\text{eq}= \frac{1}{ \left(\frac{1}{L_1}\right)+ \left(\frac{1}{L_2}\right)}\)

For two inductors, the same result can be written as:

\(\displaystyle L_\text{eq}= \frac{L_1 \times L_2}{L_1+L_2}\)

Parallel branches have the same voltage across them. Their current paths combine, so the network presents a lower ideal inductance than either branch alone. The reciprocal formula applies only where the inductors are magnetically isolated from each other.

Calculation Example

Enter:

• Inductance 1: 10 mH
• Inductance 2: 10 mH
• Inductance 3 (optional): 0 mH

Because the third entry is 0, two inductors participate:

\(\displaystyle L_\text{eq}= \frac{10 \text{ mH} \times 10 \text{ mH}} {10 \text{ mH}+10 \text{ mH}}\)

\(\displaystyle L_\text{eq}= \frac{100}{20} = \text{5 mH}\)

The expected calculator output is:

• Equivalent inductance: 5 mH
• Participating inductors: 2 count

Two equal, ideal 10 mH inductors in parallel therefore provide the same ideal parallel inductance as a single 5 mH inductor.

Circuit and Field Limits

This calculation assumes ideal, uncoupled inductors. It does not account for mutual inductance, winding polarity, a shared magnetic core, physical coil orientation, separation, DC resistance, AC loss, self-resonance, tolerance, temperature rise, or saturation.

Do not use the displayed Equivalent inductance as confirmation that parallel inductors can safely share circuit current. Each selected component must still be evaluated against its manufacturer data for DC resistance, RMS or thermal current capability, saturation-current definition, temperature rise, operating frequency, and actual circuit waveform. Inductor saturation-current specifications commonly identify the DC bias current at which inductance falls by a stated percentage, and that percentage is not universal between products.

Inductors mounted close together or wound on a common core can exchange magnetic flux. In that condition, mutual inductance changes the result, and the simple reciprocal equation is not the applicable circuit model. A coupled-inductor calculation requires coupling information that is not entered in Inductance 1, Inductance 2, or Inductance 3 (optional).