Calculators
Series & Parallel Inductor Calculator
Combine inductors in series or parallel and calculate reactance.
Combine two or more ideal uncoupled inductors in series or parallel. Optionally see the inductive reactance of the equivalent inductance at a chosen frequency.
Equivalent inductance
400 mH
Inductive reactance at 1000 Hz2513.2741 Ω
Series: Leq = L1 + L2 + …
This ideal calculation assumes the inductors are magnetically uncoupled. Nearby or wound-together coils can have mutual inductance, so their real equivalent inductance may differ.
About This Tool
Inductors are often combined to obtain an equivalent inductance that is not available as a single component or to understand how a circuit network behaves. This calculator combines two or more ideal, magnetically uncoupled inductors in either a pure series or pure parallel connection. Each value can use its own H, mH, µH, or nH unit. You can also enter a frequency to calculate the ideal inductive reactance of the resulting equivalent inductance. All calculations run locally in the browser.
How To Use It
- Choose whether the inductors are connected in series or parallel.
- Enter at least two positive inductance values and select the unit for each one. Add more rows when needed.
- Enter a non-negative frequency in hertz to see the equivalent inductor's ideal reactance at that frequency.
- Use the equivalent value as an ideal calculation only; account for coupling, resistance, parasitic capacitance, tolerance, saturation, and frequency-dependent behavior in real circuits.
Examples
100 mH and 300 mH in series
Series inductances add directly: 100 mH + 300 mH = 400 mH.
100 mH and 300 mH in parallel
The reciprocal rule gives 1/Leq = 1/100 + 1/300 in inverse millihenries, so Leq = 75 mH.
Three equal inductors
Three uncoupled 10 mH inductors equal 30 mH in series or about 3.333 mH in parallel.
Useful Notes
Series inductance formula
For ideal uncoupled inductors in series, equivalent inductance is the sum: Leq = L1 + L2 + … + Ln. Adding another positive series inductance therefore increases the total.
Parallel inductance formula
For ideal uncoupled inductors in parallel, 1/Leq = 1/L1 + 1/L2 + … + 1/Ln. The equivalent is therefore smaller than the smallest individual inductance.
Inductive reactance
For an ideal inductor under sinusoidal steady-state conditions, inductive reactance is XL = 2πfL, measured in ohms. Reactance grows with both frequency and inductance. This is not the same as the winding's DC resistance.
Why magnetic coupling matters
The simple series and parallel formulas assume no mutual inductance between coils. If magnetic fields link the inductors, mutual inductance can raise or lower the effective value depending on winding orientation and coupling. Coupled coils and transformers require a different model.
Real component limitations
Physical inductors have winding resistance, parasitic capacitance, tolerance, current limits, core losses, saturation behavior, and a self-resonant frequency. The ideal equivalent value is useful for first-pass calculations, but component datasheets and measured behavior matter in practical designs.
FAQ
Why is parallel inductance smaller than the smallest inductor?
The reciprocal contributions add. For positive uncoupled inductances, their reciprocal sum is larger than any single reciprocal, so taking the reciprocal produces a smaller equivalent value.
Can I mix mH and µH values?
Yes. Each row has its own unit selector, and the calculator converts every value to henries before combining them.
Does the calculator include mutual inductance?
No. It intentionally uses the standard uncoupled-inductor formulas. Closely spaced, shared-core, or intentionally coupled coils can require mutual-inductance terms.
Is inductive reactance the same as resistance?
No. XL = 2πfL describes ideal AC opposition associated with inductance. A real coil also has winding resistance and other frequency-dependent losses.
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