Reactance Calculator
The reactance of a capacitor/inductor at a given frequency — Xc and Xl.
What it does: Compute the capacitive reactance Xc and inductive reactance Xl at a given frequency.
When to use it: When designing filters/resonance or estimating AC impedance.
MEANS The higher the reactance, the more it "opposes" AC at that frequency. Capacitive reactance falls as frequency rises; inductive reactance rises as frequency rises.
Common cases pre-computed: browse reactance presets →
No history yet. Each calculation is automatically saved to this device.
How to use the reactance calculator
Enter the frequency plus C/L.
- 01
Enter the frequency f
The signal frequency; accepts
1k,1MHz. - 02
Enter C and/or L
Enter a capacitance for the capacitive reactance Xc, an inductance for the inductive reactance Xl, or both.
- 03
Read the reactance
Reactance is measured in ohms (Ω) and represents how much a component "opposes" AC at that frequency.
Common questions, answered in 3 minutes
Is reactance the same as resistance?
Both are measured in ohms and both oppose current, but reactance varies with frequency and dissipates no energy (it stores and releases it); resistance is frequency-independent and dissipates energy.
How does reactance change as frequency rises?
Capacitive reactance Xc decreases as frequency rises (a capacitor "passes" high frequencies more); inductive reactance Xl increases as frequency rises (an inductor "opposes" high frequencies more).
What is resonance?
The frequency where Xc=Xl is the resonant frequency, at which an LC presents a special impedance (minimum in series, maximum in parallel).
Are these ideal values?
Yes. Real capacitors have ESR/ESL and real inductors have copper resistance and parasitic capacitance, so they deviate from ideal at high frequency — check the device specs.
Standards and sources referenced by this tool
| Item | Value / Formula | Source |
|---|---|---|
| Reactance | Xc=1/(2πfC), Xl=2πfL | AC circuit theory |
AC reactance of ideal components, no external API.