MasterTool

Reactance Calculator

Calculate inductive and capacitive reactance at a frequency, plus the resonant frequency of the entered L–C pair.

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What this tool does

Calculate inductive and capacitive reactance at a frequency, plus the resonant frequency of the entered L–C pair. Components are ideal; real inductors add winding resistance and real capacitors add ESR, both of which matter near resonance.

How to use the Reactance Calculator

  1. Enter or select primary reactance.
  2. Enter or select frequency (hz).
  3. Enter or select inductance (mh).
  4. Enter or select capacitance (µf).
  5. Read the calculated result; change any measurement to compare alternatives.

Formula

XL = 2πfL; XC = 1 ÷ (2πfC)
kind
Primary reactance
frequency
Frequency (Hz)
inductance
Inductance (mH)
capacitance
Capacitance (µF)

Components are ideal; real inductors add winding resistance and real capacitors add ESR, both of which matter near resonance.

Worked example

For reactance calculator, the following measurements illustrate the exact method: Primary reactance: inductive; Frequency (Hz): 1000; Inductance (mH): 10; Capacitance (µF): 1.

Inputs

  • Primary reactanceInductive (XL)
  • Frequency (Hz)1000
  • Inductance (mH)10
  • Capacitance (µF)1

Result

  • Inductive reactance XL (ohms)62.83
  • Inductive reactance XL (ohms)62.83
  • Capacitive reactance XC (ohms)159.15
  • Resonant frequency of this L–C pair (Hz)1,591.55

Results explained

Inductive reactance XL (ohms)
Inductive reactance XL (ohms) from the formula above. Components are ideal; real inductors add winding resistance and real capacitors add ESR, both of which matter near resonance.
Inductive reactance XL (ohms)
Inductive reactance XL (ohms) from the formula above. Components are ideal; real inductors add winding resistance and real capacitors add ESR, both of which matter near resonance.
Capacitive reactance XC (ohms)
Capacitive reactance XC (ohms) from the formula above. Components are ideal; real inductors add winding resistance and real capacitors add ESR, both of which matter near resonance.
Resonant frequency of this L–C pair (Hz)
Resonant frequency of this L–C pair (Hz) from the formula above. Components are ideal; real inductors add winding resistance and real capacitors add ESR, both of which matter near resonance.

Frequently asked questions

XL = 2πfL. A 10 mH inductor at 1 kHz has XL = 2π × 1,000 × 0.01 ≈ 62.8 Ω, and XL rises in direct proportion to frequency.

XC = 1 ÷ (2πfC). A 1 µF capacitor at 1 kHz has XC ≈ 159 Ω, and XC falls as frequency rises — the opposite behaviour to an inductor.

At the resonant frequency f = 1 ÷ (2π√(LC)) of the pair, where the two reactances are equal and the series impedance is purely resistive.

No. Reactance opposes AC current like resistance but stores and returns energy instead of dissipating it, and it shifts the current's phase by 90°.

Frequency in hertz, inductance in millihenrys and capacitance in microfarads — the conversions to henrys and farads happen inside the formula.