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Inductor Calculator (XL = 2 pi f L)

Quick answer

This calculator computes inductive reactance XL = 2 x pi x f x L, energy E = LI2/2, and voltage drop.

  • Enter any two of inductance, current, and frequency for instant results.

Figures are estimates from this calculator’s standard formula — adjust the inputs in the tool below for your exact number.

How the Inductor Calculator Works

E = ½LI², XL = 2πfL

Calculates energy stored in an inductor's magnetic field and its reactance at a given frequency. Inductors store energy proportional to current squared and oppose changes in current. Worked example: a 10 mH choke at 60 Hz has XL = 2 pi x 60 x 0.01 = 3.77 ohm, but at 10 kHz it rises to 628 ohm - which is why chokes block ripple yet pass DC. At radio frequencies the same coil behaves differently: 10 mH at 1 MHz presents XL = 62.8 kohm, which is why chokes that ignore audio barely notice RF and vice versa.

  1. 1

    Step 1

    Enter the inductance value (L)

  2. 2

    Step 2

    Enter the current through the inductor

  3. 3

    Step 3

    Optionally enter frequency for reactance calculation

  4. 4

    Step 4

    View stored energy and inductive reactance

Use Cases

Designing switch-mode power supplies

Calculating energy storage in DC-DC converters

Sizing inductors for filter circuits

Analyzing flyback transformer operation

Tips

  • 1

    Energy stored is proportional to current squared

  • 2

    Inductors resist sudden current changes

  • 3

    Saturation current limits maximum energy storage

  • 4

    DC resistance affects efficiency in power applications

Common Mistakes

  • Ignoring inductor saturation current limits

  • Forgetting DC resistance losses

  • Not considering core material frequency limits

  • Using inductors beyond their self-resonant frequency

FAQs

Why does energy depend on current squared?

The magnetic field energy is proportional to the square of the magnetic flux, which is proportional to current. Doubling current quadruples the stored energy.

What is inductor saturation?

Saturation occurs when the core material cannot hold more magnetic flux. Above the saturation current, inductance drops dramatically, reducing energy storage and potentially causing circuit failure.

How do I choose between air-core and ferrite-core inductors?

Air-core inductors have no saturation but lower inductance. Ferrite cores provide higher inductance in smaller packages but saturate at specific current levels. Choose based on current requirements and frequency.

How do I calculate inductive reactance?

XL = 2 x pi x f x L. A 1 mH coil at 50 Hz is only 0.31 ohm but 6.28 ohm at 1 kHz. Reactance scales linearly with both frequency and inductance.

Why does an inductor block AC but pass DC?

At DC, f = 0 so XL = 0: the coil is just its winding resistance. As frequency rises the changing current induces a counter-EMF that opposes current - the inductor resists change, not flow.

How much energy does an inductor store?

E = L x I2 / 2. A 100 mH coil at 2 A stores 0.2 J; releasing that into a 12 V clamp takes 17 ms average. This stored energy is what generates voltage spikes when switching inductive loads.

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