Electrónica

Inductive & Capacitive Reactance Calculator: XL and XC

Calculate inductive reactance XL = 2πfL and capacitive reactance XC = 1/(2πfC) for any frequency, inductance, and capacitance. Shows resonance, XL/XC ratio, and circuit behavior instantly.

🗓️ Updated June 2026 Reviewed by Martín Rodríguez

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Reviewed by: Martín Rodríguez (editorial policy ) · Last reviewed: Jun 22, 2026

Component(s) to Calculate*

Frequency (Hz)*

Inductance (mH)

Capacitance (µF)

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Inductive reactance (XL) and capacitive reactance (XC) are the AC opposition offered by inductors and capacitors at a given frequency. Unlike resistance, reactance does not dissipate energy — it stores and returns it each cycle. Use this calculator to compute XL = 2πfL and XC = 1/(2πfC) instantly, compare them, and identify whether your circuit is inductively dominant, capacitively dominant, or at resonance. Essential for filter design, RF circuits, audio crossovers, and power electronics.

When to use this calculator

Design LC filters (low-pass, high-pass, band-pass) for audio and RF
Calculate resonant frequency and verify crossover networks
Validate inductor and capacitor choices before building circuits
Teach AC circuit theory (phase shift, impedance, resonance)
Troubleshoot oscillation or noise issues in microcontroller projects (Arduino, ESP32)

XL vs XC at Common Frequencies (L = 10 mH, C = 1 µF)

Frequency (Hz)	XL — 10 mH (Ω)	XC — 1 µF (Ω)	Dominant
100	6.28	1,591.5	Capacitive
500	31.42	318.3	Capacitive
1,000	62.83	159.2	Capacitive
1,591.5	100.0	100.0	Resonance (XL = XC)
5,000	314.2	31.83	Inductive
10,000	628.3	15.92	Inductive
100,000	6,283	1.59	Inductive

Fuente: All About Circuits — Reactance and Impedance (allaboutcircuits.com). Values derived from XL = 2πfL and XC = 1/(2πfC). Resonant frequency f₀ = 1/(2π√LC) ≈ 1,591.5 Hz for these component values.

How it works

XL and XC Formulas

Reactance is frequency-dependent opposition to AC current. For a pure inductor or capacitor it creates a 90° phase shift — no energy is dissipated as heat (unlike resistance). In real components, a small resistive loss always exists, characterized by the Q factor (quality factor), but for most circuit calculations at audio and RF frequencies, the ideal model is sufficient.

Inductive Reactance:

> XL = 2π × f × L

f: frequency in Hz

L: inductance in henries (mH × 0.001; µH × 0.000001)

XL grows linearly with frequency. At DC (f = 0), XL = 0 — an inductor is a short circuit. At very high frequency, XL becomes large — inductors block high frequencies and pass low frequencies. This is the operating principle behind chokes in power supplies and RF noise filters.

Capacitive Reactance:

> XC = 1 / (2π × f × C)

C: capacitance in farads (µF × 0.000001; nF × 0.000000001)

XC falls inversely with frequency. At DC, XC → ∞ — a capacitor is an open circuit and blocks DC completely. At very high frequency, XC → 0. Capacitors block low frequencies and pass high frequencies, which is why they are used as coupling and bypass components in amplifier stages.

How to Calculate — Step by Step

Example: XL for a 47 mH inductor at 1 kHz

1. Convert: L = 47 mH = 0.047 H
2. XL = 2π × 1,000 × 0.047
3. XL = 6.2832 × 47 = 295.3 Ω

Example: XC for a 100 nF capacitor at 10 kHz

1. Convert: C = 100 nF = 0.0000001 F = 1 × 10⁻⁷ F
2. XC = 1 / (2π × 10,000 × 0.0000001)
3. XC = 1 / 0.006283 = 159.2 Ω

XL vs XC at Common Frequencies — Reference Table

Using L = 10 mH, C = 1 µF:

Frequency	XL (10 mH)	XC (1 µF)	Dominant
100 Hz	6.28 Ω	1,591.5 Ω	Capacitive
500 Hz	31.42 Ω	318.3 Ω	Capacitive
1,000 Hz	62.83 Ω	159.2 Ω	Capacitive
1,591.5 Hz	100.0 Ω	100.0 Ω	Resonance
5,000 Hz	314.2 Ω	31.83 Ω	Inductive
10,000 Hz	628.3 Ω	15.92 Ω	Inductive
100,000 Hz	6,283 Ω	1.59 Ω	Inductive

At resonance (1,591.5 Hz for these values), XL = XC and the net reactance cancels to zero — impedance is purely resistive and equals only the circuit's ohmic resistance.

Resonant Frequency

> f₀ = 1 / (2π × √(L × C))

This is where XL = XC. In a series LC circuit, resonance means minimum impedance and maximum current — used in bandpass filters and series-tuned traps. In a parallel LC circuit, resonance means maximum impedance — used in tank circuits in oscillators and narrowband RF amplifiers. AM radio tuning is a direct application: varying C shifts f₀ to select a station.

Phase Shift

Inductor: current lags voltage by 90°. Memory aid: "ELI" — in an L-circuit, E (voltage) comes before I (current).

Capacitor: current leads voltage by 90°. Memory aid: "ICE" — in a C-circuit, I (current) comes before E (voltage).

This 90° relationship is exact only for ideal components. Real inductors have winding resistance (ESR) and parasitic capacitance; real capacitors have equivalent series resistance (ESR) and lead inductance. Both reduce the effective phase angle below 90°.

Impedance in Series RLC Circuits

When resistance R is also present, total impedance is:

> Z = √(R² + (XL − XC)²)

Reactance values alone (XL, XC) are not the full story in real circuits — R always exists and limits minimum impedance at resonance.

Common Errors

Unit confusion: Plugging mH or µF directly without converting to H or F is the most frequent calculation mistake. Always convert to base SI units first.

Confusing reactance with impedance: XL and XC are the reactive components only. Total impedance Z includes resistance.

Assuming ideal behavior at all frequencies: Inductor self-resonance (SRF) occurs when winding capacitance resonates with inductance — above SRF, the component behaves capacitively. Always check the component datasheet SRF for RF applications.

Forgetting DC behavior: XC at DC is infinite (open circuit); XL at DC is zero (short circuit). These boundary conditions are useful sanity checks.

What This Calculator Does NOT Cover

Q factor and component losses (requires ESR data)

Skin effect in inductors at high frequency, which increases effective resistance

Impedance matching calculations (use a dedicated Smith chart tool)

Three-phase AC reactance (same formulas apply per phase, but circuit topology differs)

Worked Example: L = 10 mH, C = 1 µF at f = 1 kHz

XL = 2π × 1,000 Hz × 0.010 H = 62.83 Ω

XC = 1 / (2π × 1,000 Hz × 0.000001 F) = 159.15 Ω

XL/XC = 62.83 / 159.15 = 0.395 — capacitive dominance

Resonant frequency f₀ = 1 / (2π × √(0.010 × 0.000001)) = 1,591.5 Hz

XL = 62.83 Ω, XC = 159.15 Ω. At 1 kHz the circuit is capacitively dominant. Raise frequency to 1,591.5 Hz for resonance.

Frequently asked questions

What is inductive reactance (XL)?

Inductive reactance XL is the opposition an inductor offers to alternating current at a given frequency. It equals 2π × f × L. Unlike resistance, XL does not dissipate energy — it stores energy in a magnetic field and returns it each cycle. XL increases linearly as frequency rises.

What is capacitive reactance (XC)?

Capacitive reactance XC is the opposition a capacitor offers to AC. It equals 1 / (2π × f × C). XC decreases as frequency rises — capacitors block DC (XC → ∞ at f = 0) and pass high-frequency signals easily.

What is the difference between reactance and resistance?

Resistance dissipates energy as heat (P = I²R). Reactance stores energy in a magnetic (inductor) or electric (capacitor) field and returns it without dissipation. Reactance also causes a 90° phase shift between voltage and current; resistance causes no phase shift.

How do I calculate resonant frequency from XL and XC?

At resonance XL = XC. Solving gives f₀ = 1 / (2π × √(L × C)). For example, L = 10 mH and C = 1 µF gives f₀ = 1 / (2π × √(0.01 × 0.000001)) ≈ 1,591.5 Hz. At this frequency in a series circuit, impedance is minimum.

What happens to XL and XC at DC (0 Hz)?

At DC: XL = 0 (inductor acts as a short circuit — only wire resistance remains). XC = ∞ (capacitor acts as an open circuit — fully blocks DC). This is why capacitors are used for DC blocking and inductors for DC chokes.

Is reactance the same as impedance?

No. Impedance Z combines resistance and reactance: Z = R + j(XL − XC), or |Z| = √(R² + (XL−XC)²). For a pure inductor Z = jXL; for a pure capacitor Z = −jXC. Impedance is the complete AC opposition including phase information.

Why does XL increase with frequency but XC decrease?

An inductor opposes changes in current (Lenz's law). Faster changes (higher frequency) mean greater opposition, so XL = 2πfL rises with f. A capacitor opposes changes in voltage but charges and discharges faster at higher frequencies, offering less opposition: XC = 1/(2πfC) falls with f.

How do I use this to design a simple low-pass LC filter?

Choose a cutoff frequency f₀. At f₀ the inductor and capacitor swap roles: the inductor passes frequencies below f₀ (low XL) and the capacitor shunts high frequencies to ground (low XC). Use f₀ = 1/(2π√LC) to pick L and C values that set the cutoff. Check XL and XC values with this calculator to confirm component choices.

What units does this calculator use?

Frequency in Hz, inductance in millihenries (mH), capacitance in microfarads (µF). Results are in ohms (Ω), automatically scaled to kΩ or MΩ for large values. The calculator internally converts mH to H (×0.001) and µF to F (×0.000001).

Sources & references

Methodology & trust

Editorial

Calculadora de electrónica revisada por el equipo editorial de Hacé Cuentas, contrastada con All About Circuits — Reactance and Impedance — Inductive, según nuestra política editorial y metodología.

Updates

Última revisión: June 22, 2026. Los parámetros se verifican periódicamente con las fuentes citadas.

Privacy

Calculations run 100% in your browser. We do not store or transmit your data.

Limitations

Indicative results. For critical decisions, consult a professional.

📌 How to cite this calculator

Rodríguez, M. (2026). Inductive & Capacitive Reactance Calculator: XL and XC. Hacé Cuentas. https://hacecuentas.com/inductive-capacitive-reactance

Contenido bajo licencia CC-BY 4.0 — reutilizable citando la fuente con enlace a Hacé Cuentas.

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