Inductive Reactance Calculator
Inductive reactance (XL) measures how much an inductor opposes alternating current at a given frequency. The formula XL = 2 * pi * f * L shows that reactance is directly proportional to both frequency and inductance. At higher frequencies, an inductor appears more resistive to AC signals, making inductors useful as high-frequency filters and chokes. Enter the frequency in hertz and the inductance in henries. For common conversions: 1 millihenry (mH) = 0.001 H, 1 microhenry (uH) = 0.000001 H, 1 kilohertz (kHz) = 1,000 Hz.
Inductive reactance formula
XL = 2 * pi * f * L
Where f is frequency in hertz (Hz) and L is inductance in henries (H). The result XL is in ohms. Example: 10 mH at 60 Hz gives XL = 2 * 3.14159 * 60 * 0.01 = 3.77 ohms.
Inductive reactance in circuit design
- Power line filter chokes (inductors) use high XL at high frequencies to block noise while passing 60 Hz power.
- In LC resonant circuits, XL equals XC (capacitive reactance) at the resonant frequency, resulting in maximum current flow.
- RF chokes have very high XL at radio frequencies, isolating DC supply lines from RF signals.
- Transformers rely on inductive reactance to transfer energy between windings via a shared magnetic field.
Frequently asked questions
What is inductive reactance?
Inductive reactance (XL) is the opposition an inductor offers to alternating current. Unlike resistance, it does not dissipate energy but stores it in a magnetic field. XL is measured in ohms and increases with frequency.
What is the inductive reactance formula?
XL = 2 * pi * f * L, where f is frequency in hertz and L is inductance in henries. For example, a 10 mH inductor at 1 kHz has XL = 2 * pi * 1,000 * 0.01 = 62.83 ohms.
Why does inductive reactance increase with frequency?
Higher frequency means faster-changing current. An inductor opposes changes in current more strongly the faster those changes occur. At DC (f = 0), inductive reactance is zero; the inductor acts as a short circuit for DC.
How does inductive reactance differ from resistance?
Resistance dissipates energy as heat. Inductive reactance stores energy in a magnetic field and returns it each cycle, causing current to lag voltage by 90 degrees in a purely inductive circuit.
What is the relationship between XL and impedance?
For a series RL circuit, impedance Z = sqrt(R^2 + XL^2). The phase angle is theta = arctan(XL / R). Impedance combines both energy dissipation (R) and reactive energy storage (XL).
Official sources
- NIST: NIST SP 811, Guide for SI Units.
- OpenStax University Physics: Simple AC Circuits, Vol. 2 Ch. 15.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.