Inductor Impedance Calculator | Inductive Reactance XL = 2πfL

How to use inductor impedance calculator

To use the calculator enter two values. The blank field will be automatically calculated. If you fill in all three fields, the last calculated value will be recalculated. You can modify the units using the selectors.

Impedance of an inductor

An inductor is a circuit passive component that stores energy (in the form of a magnetic field) for short periods of time. The quantity that describes an inductor is the inductance, and is given in Henries [H]. For 'small' electronics, a Henry is a lot, so it is usual to give it in 'millis', 'micros', 'nanos'... The main characteristic of an inductor is that its impedance varies as a function of frequency. In a way, you can understand it as a resistor that changes its value according to the frequency of the wave in the circuit. This last sentence hides some little lies, but, in general, you can see it like this. For very high frequencies, the impedance is huge. At high enough frequencies, you can consider it as an open circuit. For low frequencies, the opposite is true, its impedance is very low. In DC, it is a short circuit. By combining inductors and other elements, filters can be made that select or reject certain frequencies. The equation that describes the impedance of an inductor as a function of the frequency is:

$$Z[Ω] = 2\cdot \pi \cdot f \cdot L$$

On this page we have talked about inductors. This is the name given to the theoretical element of a circuit. The physical object is called 'coil' because it consists of a wire wound around a core. By abuse of language, they are sometimes interchanged, but depending on the context, it may be necessary to speak properly.

If this inductor is part of a filter, try the low-pass filter calculator next. It also helps to compare the frequency trend with the capacitor impedance calculator when you are matching L and C behavior.

Example

What is the inductance a coil must have if I want its impedance to be 10[Ω] at 125 k[Hz]?

• To calculate the inductance, we use the above equation but we solve for this variable:$$L = \frac{Z}{2\cdot \pi \cdot f} = $$ $$= \frac{10}{2\cdot \pi \cdot 125000} = $$ $$= 0.00001273 [H] = 12.73 µ[H]$$

Frequently Asked Questions

• How does frequency affect inductor impedance?
  Inductor impedance increases with frequency. This makes inductors useful for blocking high-frequency signals while allowing DC (zero frequency) to pass through.
• What is the main difference between an ideal and a real inductor?
  An ideal inductor has zero resistance and capacitance. Real inductors (coils) have wire resistance and parasitic capacitance between turns, which can cause resonance at very high frequencies and allow AC signal to pass through it.
• Can I use this calculator for RF (Radio Frequency) coils?
  Yes, but be aware that at RF frequencies, parasitic capacitance becomes significant. If the frequency is near the coil's self-resonant frequency, the simple impedance formula used here may not be accurate.