〰️ Reactance Calculator (Xc & Xʟ)
Enter a frequency and a capacitance or inductance to get its reactance, the frequency-dependent AC opposition in ohms.
Capacitive reactance Xc
159.2 Ω
Capacitive reactance Xc = 1 ÷ (2πfC) falls as frequency rises, a capacitor passes high frequencies and blocks DC. Reactance is the frequency-dependent AC "resistance" of the component, in ohms. 🔒 In your browser.
How the reactance calculator (xc & xʟ) works
Reactance is the opposition a capacitor or inductor presents to alternating current, measured in ohms but varying with frequency. Capacitive reactance is Xc = 1 ÷ (2πfC): it falls as frequency rises, so a capacitor blocks DC and passes high frequencies. Inductive reactance is Xʟ = 2πfL: it rises with frequency, so an inductor passes DC and opposes high frequencies. Pick the component type, enter the frequency and the capacitance or inductance (with convenient units), and the tool returns the reactance. The 2πf term converts the frequency in hertz to angular frequency in radians per second, which is why reactance scales directly with frequency for an inductor and inversely for a capacitor. Worked example: a 100 nF capacitor at 50 Hz has Xc = 1 ÷ (2π × 50 × 100×10⁻⁹) ≈ 31.8 kΩ, while a 100 mH inductor at the same 50 Hz has Xʟ = 2π × 50 × 0.1 ≈ 31.4 Ω.
Reactance is the imaginary part of impedance; in a circuit with resistance too, the total opposition is the impedance Z = √(R² + X²). At the resonant frequency of an LC pair the capacitive and inductive reactances are equal and cancel, see the LC resonant-frequency calculator.
Frequently asked questions
How do I calculate capacitive reactance?
Xc = 1 ÷ (2πfC), with f in hertz and C in farads. A 1 µF capacitor at 1 kHz has a reactance of about 159 Ω. Doubling the frequency halves the reactance.
How do I calculate inductive reactance?
Xʟ = 2πfL, with f in hertz and L in henries. A 10 mH inductor at 1 kHz has a reactance of about 63 Ω. Doubling the frequency doubles the reactance.
What is the difference between reactance and resistance?
Resistance opposes current the same at all frequencies and dissipates power as heat. Reactance opposes alternating current in a frequency-dependent way and stores energy (in a capacitor's field or an inductor's field) rather than dissipating it.
Why does capacitor reactance decrease with frequency?
A capacitor charges and discharges more times per second as frequency rises, so more current flows for the same voltage, which means lower reactance. At DC (0 Hz) its reactance is infinite, blocking current entirely.
What is impedance versus reactance?
Impedance Z combines resistance R and reactance X into the total opposition to AC: Z = √(R² + X²) in magnitude. Reactance is just the part contributed by capacitors and inductors; this tool gives that reactance.
What is the reactance of a component at DC?
At 0 Hz an inductor's reactance is zero (it behaves like a plain wire), while a capacitor's reactance is infinite (it blocks steady current once charged). This is why capacitors block DC and inductors pass it.
Does reactance dissipate power like resistance?
No, an ideal reactance stores and returns energy each AC cycle rather than turning it into heat, so it draws no net (real) power. Only the resistive part of an impedance dissipates power; reactance contributes reactive power measured in VARs.
How do I combine reactance with resistance?
Use the impedance magnitude Z = √(R² + X²). For a resistor and capacitor in series with R = 40 Ω and Xc = 30 Ω, Z = √(40² + 30²) = 50 Ω. Reactance and resistance add as perpendicular components, not directly.