Inductor Network Calculator

This inductor network calculator combines up to five inductors connected in series or parallel into a single equivalent inductance (L_eq). If you also provide a current value, it estimates the magnetic energy stored in that equivalent inductance. It’s a practical helper when you are selecting standard parts to hit a target inductance, sanity-checking a prototype, or comparing series vs. parallel arrangements in filters, resonant tanks, and power electronics.

Introduction: What the calculator outputs

• Equivalent inductance of the network (L_eq, in henries).
• Stored energy (optional) if you enter current (E, in joules), computed from L_eq and I.

Units and entering values

Inductance is measured in henries (H), but most real inductors are specified in smaller units:

• 1 mH = 10⁻³ H
• 1 µH = 10⁻⁶ H
• 1 nH = 10⁻⁹ H

Enter all inductors in henries. Examples:

• 47 µH = 47 × 10⁻⁶ H = 0.000047 H
• 2.2 mH = 2.2 × 10⁻³ H = 0.0022 H

Formulas used

The calculator treats the set of inductors as an ideal series or ideal parallel network (see limitations below). Use the formulas that match your wiring:

Inductors in series

For series inductors, the same current flows through each inductor and the voltages add. The equivalent inductance is the sum:

In plain terms: add up every non-blank inductor value you entered.

Inductors in parallel

For parallel inductors, each branch sees the same voltage and the current splits among branches. The reciprocals add:

1 / L_eq = Σ (1 / L_i)

Then:

L_eq = 1 / Σ (1 / L_i)

Energy stored (optional)

If you enter a current, the tool estimates stored magnetic energy using the equivalent inductance:

E = ½ · L_eq · I²

Where E is joules (J), L_eq is henries (H), and I is amperes (A).

How to interpret the results

• Series increases inductance: adding inductors in series increases L_eq linearly (two identical inductors in series → double the inductance).
• Parallel decreases inductance: adding parallel branches decreases L_eq (two identical inductors in parallel → half the inductance).
• Energy depends strongly on current: because energy scales with I², doubling current quadruples stored energy for the same L_eq.

Worked example (parallel + energy)

Three inductors in parallel:

• L₁ = 10 mH = 0.010 H
• L₂ = 20 mH = 0.020 H
• L₃ = 40 mH = 0.040 H

Compute the reciprocal sum:

• 1/L₁ = 1/0.010 = 100 H⁻¹
• 1/L₂ = 1/0.020 = 50 H⁻¹
• 1/L₃ = 1/0.040 = 25 H⁻¹

Sum = 100 + 50 + 25 = 175 H⁻¹

Take the reciprocal:

L_eq = 1 / 175 ≈ 0.005714 H = 5.714 mH

If the network current is I = 2 A, the stored energy estimate is:

E = ½ · 0.005714 · (2)² = 0.5 · 0.005714 · 4 ≈ 0.011428 J

So the network stores about 0.0114 joules at 2 A under the ideal assumptions below.

Series vs. parallel: quick comparison

Assumptions and limitations (important)

• Ideal inductors: ignores winding resistance (DCR), core losses, parasitic capacitance, and skin/proximity effects.
• No mutual coupling: assumes inductors do not magnetically couple. If coils are near each other or share a core, coupling can increase or decrease the effective inductance and the simple series/parallel rules may not apply.
• No saturation: real inductors lose inductance as current increases toward saturation. The energy result is an estimate and can be optimistic at high current.
• Frequency dependence not modeled: inductance and losses can vary with frequency; for RF or fast-switching converters, parasitics can dominate.
• Tolerance not included: component tolerances (e.g., ±10%, ±20%) and temperature drift can materially change the true equivalent inductance.
• Parallel edge cases: extremely small entered inductance values (approaching 0 H) will dominate the reciprocal sum and drive L_eq toward 0. Physically, this corresponds to a near-short inductive reactance at the modeled frequency, which is rarely “ideal.”
• Using fewer than five inductors: leave unused fields blank; only the values you enter should be considered part of the network.

If you need accuracy for tightly-coupled inductors, gapped cores, or high-current designs, treat these results as a first-pass calculation and validate with datasheets, measurement, and (when applicable) a coupled-inductor model.

How to use this calculator

1. Enter Configuration using the unit or time period shown by the field.
2. Enter Inductor L1 (H) using the unit or time period shown by the field.
3. Enter Inductor L2 (H) using the unit or time period shown by the field.
4. Run the calculation and compare the output with a second scenario before acting on it.