Inductor Series Value Calculator

The Inductor Series Value Calculator determines the ideal equivalent inductance produced when separate inductors are connected in series. The calculated value is the total inductance seen by the circuit at the series connection, expressed in millihenries (mH).

Series inductors are commonly reviewed when selecting or combining inductive components in filters, chokes, relay circuits, timing networks, power-conversion circuits, and other low- or high-frequency electronic equipment. The equivalent inductance can be used to compare a proposed series arrangement with a required target inductance before selecting parts or completing a circuit calculation.

The calculator returns one value:

Result	Electrical meaning
Equivalent inductance	The ideal total inductance of the entered inductors connected in series

Inductance Inputs

Enter the component values using the calculator’s actual input fields:

Input	Required	Entry requirement
Inductance 1	Yes	Enter the first positive inductance
Inductance 2	Yes	Enter the second positive inductance
Inductance 3 (optional)	No	Enter a positive third inductance, or enter 0 to omit it

All entered values use mH. The result is also displayed in mH.

Inductance 1 and Inductance 2 represent the two required series components. Inductance 3 (optional) lets a third inductor be included without changing the calculation method. A value of 0 for the optional field does not add inductance to the result.

Series Inductance Formula

For ideal inductors connected in series, inductance adds directly:

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

Where:

• \(L_{\text{eq}}\) = equivalent inductance
• \(L_1\) = Inductance 1
• \(L_2\) = Inductance 2
• \(L_3\) = Inductance 3 (optional)

When Inductance 3 (optional) is entered as 0, the equation becomes:

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

Unlike capacitors in series, ideal inductor values in a series path increase by direct addition.

Calculation Example

Enter the following values:

Field	Value
Inductance 1	10 mH
Inductance 2	10 mH
Inductance 3 (optional)	0 mH

\(\displaystyle L_{\text{eq}} = 10\text{ mH} + 10\text{ mH} + 0\text{ mH}\)

\(\displaystyle \boxed{L_{\text{eq}} = 20\text{ mH}}\)

The calculator result is Equivalent inductance: 20 mH.

In an ideal circuit, the two 10 mH inductors behave as one 20 mH inductance when connected in series with the same current flowing through both components.

Circuit and Field Limits

The calculation assumes ideal inductors with no interaction between their magnetic fields. Actual circuit performance may differ from the calculated equivalent inductance when inductors are mounted close enough for magnetic coupling, wound on a shared core, or positioned so their fields affect one another.

Component selection and circuit verification must separately account for:

• Inductor tolerance and the actual measured inductance at the operating condition
• DC resistance and associated voltage drop or heat loss
• Current rating and core saturation under expected load current
• Frequency-dependent losses, parasitic capacitance, and self-resonant behavior
• Physical lead routing, polarity markings where applicable, and spacing between magnetic components
• The effect of the combined inductance on circuit current, switching behavior, filtering, or resonance

The calculator provides the ideal series inductance value. It does not determine current capacity, thermal performance, saturation margin, voltage rating, or whether the selected components are suitable for a specific electronic assembly.