Inductance Converter and Inductive Reactance Calculator

Inductance is the property of an electrical conductor by which a change in current induces an electromotive force (EMF) in the conductor itself (self-inductance) or in a nearby conductor (mutual inductance). The henry (H) is the SI unit of inductance, defined as the inductance of a circuit in which a change of current of one ampere per second produces an EMF of one volt. It is named after Joseph Henry, who independently discovered electromagnetic induction alongside Michael Faraday.

Inductive reactance (XL) is the opposition that an inductor presents to alternating current, measured in ohms (Ω). Unlike resistance, inductive reactance stores energy in a magnetic field rather than dissipating it as heat. It is calculated as XL = 2 * π * f * L, where f is the frequency in hertz and L is the inductance in henries. Inductive reactance increases proportionally with frequency, so an inductor passes low-frequency signals more easily than high-frequency ones.

Inductive reactance is directly proportional to both frequency and inductance. As frequency doubles, XL doubles; as inductance doubles, XL doubles. This frequency-dependent behaviour is why inductors are used as low-pass filters, blocking high-frequency signals while allowing lower frequencies to pass. The crossover frequency where XL equals the circuit resistance is called the inductive corner frequency.

Self-inductance describes how a changing current in a conductor induces a voltage in that same conductor, opposing the change (Lenz's law). Mutual inductance describes how a changing current in one conductor induces a voltage in a nearby conductor through their shared magnetic flux. Mutual inductance is the operating principle behind transformers and wireless power transfer systems. Both are measured in henries.

Inductance is typically measured using an LCR meter, which applies a known AC signal to the component and measures the resulting impedance. The inductance is then calculated from the frequency and the reactive portion of the impedance. For precision measurements, impedance analysers operating over a range of frequencies are used. Component datasheets list inductance values at a specific test frequency (commonly 1 kHz for larger inductors and 10 MHz or higher for RF inductors) because inductance can vary with frequency.