Inductor Reactance Calculator

Inductive reactance calculator (XL) for AC circuits

An inductor resists changes in current, so in an AC circuit it behaves like a frequency-dependent opposition rather than a fixed resistance. That opposition is called inductive reactance, written as XL, and it is measured in ohms (Ω). The key practical point is simple: as frequency goes up, inductive reactance goes up. That is why inductors can block high-frequency noise, shape filters, and limit current in AC systems without wasting power like a resistor would.

This calculator converts your inductance and frequency into inductive reactance using the standard engineering relationship XL = 2πfL. You can enter inductance in henries, millihenries, or microhenries, and frequency in hertz. The result is the reactance magnitude at that frequency. If you also enter an optional second frequency, the calculator will show how the reactance changes and by what factor, which is useful when you are comparing 50 Hz and 60 Hz mains, checking the effect of switching frequency, or estimating filter behavior across a band.

Use the output as a sanity check during design and troubleshooting. If your inductor is supposed to act like a strong blocker at a certain frequency, you want XL to be large compared with the other impedances in the circuit. If you need current to flow easily, you want XL to be small compared with the other impedances. This is a magnitude-only view, which is usually what you need for quick sizing and checks before you move to full impedance and phase calculations.

Assumptions and how to use this calculator

• Ideal inductor model: the calculation uses XL = 2πfL and ignores winding resistance (DCR), core losses, and parasitic capacitance.
• Frequency is treated as a single steady value. For non-sinusoidal waveforms, use the dominant frequency or analyze harmonics separately.
• Inductance is assumed constant at the operating current and frequency. Real inductors can change value due to saturation and material effects.
• Results are magnitudes in ohms. The inductor impedance is reactive (jXL), so phase and power factor effects are not computed here.
• If you enter a second frequency, the calculator compares the two reactances assuming the same inductance value.

Common questions

What is inductive reactance in plain language?

Inductive reactance is how strongly an inductor opposes AC current. It is not a real resistance that turns power into heat in the ideal model. Instead, it comes from energy being stored in and released from the magnetic field. Higher frequency makes it harder for current to change quickly, so XL increases with frequency.

Why does XL increase linearly with frequency?

Because XL is proportional to frequency in the formula XL = 2πfL. Doubling the frequency doubles XL. This is why inductors are often used as chokes: they allow low-frequency or DC components through more easily, while opposing higher-frequency components more strongly.

Should I use 50 Hz or 60 Hz for mains calculations?

Use the actual mains frequency for your region and system. Many places use 50 Hz, while others use 60 Hz. If you are designing for both, use the compare frequency field to see the difference. Reactance at 60 Hz will be 60/50 = 1.2 times the reactance at 50 Hz for the same inductor.

My inductor has a rated inductance, but the real circuit behaves differently. Why?

Real inductors include winding resistance and losses, and the inductance can shift with temperature, current level, and frequency. If the core starts to saturate at higher current, the effective inductance drops, which reduces XL and can cause higher current than expected. Use this calculator as a starting point, then cross-check with datasheet curves and measured values when precision matters.

How do I use XL to estimate current in a simple AC circuit?

For a rough magnitude estimate, you can treat XL like an impedance magnitude and use I ≈ V / XL if the inductor is the main impedance in series. In real circuits, you must include other resistances and reactances (such as resistor values, capacitor reactance, and source impedance). This calculator gives you the XL piece so you can combine it with the rest of the circuit model.