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Inductor Impedance Calculator

Enter the frequency and inductance to get the inductive reactance.

How it is calculated

The tool computes inductive reactance XL = 2π × f × L, where f is the frequency in hertz and L the inductance in henries. The answer is in ohms, rounded to two decimals. Reactance grows in direct proportion to both values: doubling the frequency or the inductance doubles XL. At 0 Hz (DC) the reactance is 0 Ω, so an ideal coil passes DC freely. Neither input can be negative. This is the reactance of an ideal inductor only. It does not include the wire resistance of a real coil, its parasitic capacitance, or core losses, which matter more at high frequency and would add to the total impedance.

Worked example

A 10 mH inductor carries a 1 kHz signal. Convert the units first: 10 mH = 0.01 H and 1 kHz = 1000 Hz. Then XL = 2π × 1000 × 0.01 = 62.83 Ω. If the frequency doubles to 2 kHz, the reactance doubles to 125.66 Ω, and at 0 Hz it falls to 0.00 Ω. With a 5 V AC signal and ignoring other resistance, the current would be about 5 / 62.83 = 0.08 A.

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Common mistakes

  • Entering inductance in millihenries or microhenries. The field takes henries, so 10 mH must be typed as 0.01; entering 10 gives a result a thousand times too large.
  • Entering the frequency in kHz or MHz. The field takes hertz, so 1 kHz is 1000.
  • Using angular frequency (rad/s) as f. The 2π is already in the formula, so entering ω counts it twice.
  • Treating the reactance as a resistance in a DC circuit. At DC the coil's XL is zero; only its wire resistance limits the current.
  • Adding reactance and resistance directly. In an AC circuit they combine as √(R² + XL²), not as a plain sum.

About this calculator

An inductor opposes changes in current with inductive reactance, XL = 2πfL, where f is the AC signal frequency (Hz) and L is inductance (henries). Unlike a resistor, reactance isn't a fixed opposition — it scales directly with frequency, so the same coil behaves almost like a short circuit at DC (f = 0) and like an open circuit at very high frequencies.

This frequency-dependent behavior is why inductors are used in filters (blocking high frequencies while passing low ones), chokes, and impedance-matching networks. Electronics engineers calculate XL when designing filter cutoff points or predicting how a circuit's impedance shifts across a frequency range.

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