Inductive Reactance Calculator (XL)
Choose what to solve for, then enter the other two values with their units. The calculator uses XL = 2π f L and shows the answer in a convenient unit.
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Formula
XL = 2 × π × f × L
Rearranged: f = XL / (2 × π × L) and L = XL / (2 × π × f). Use f in hertz, L in henries and XL in ohms; the calculator converts your units first. Only the two inputs needed for the chosen mode are used.
Worked example
A 10 mH coil at 1 kHz:
XL = 2π × 1000 × 0.01 = 62.83 Ω
Other checks: 1 µH at 10 MHz also gives 62.83 Ω. A reactance of 100 Ω at 1 kHz needs 15.915 mH, and 100 Ω with a 10 mH coil happens at 1.5915 kHz.
Frequently asked questions
What is the inductive reactance formula?
XL = 2π × f × L, with f in hertz and L in henries, gives XL in ohms. For 10 mH at 1 kHz: 2π × 1000 × 0.01 = 62.83 Ω.
Why does reactance rise with frequency?
An inductor resists changes in current, and faster changes meet more opposition. The same 10 mH coil is 62.83 Ω at 1 kHz and 628.3 Ω at 10 kHz. At DC (0 Hz) the reactance is 0 Ω, so an ideal coil passes DC freely.
How do I find the inductance for a target reactance?
Choose Inductance L as the unknown. To get 100 Ω at 1 kHz you need L = 100 / (2π × 1000) = 15.915 mH.
How does XL differ from Xc?
XL grows with frequency and makes current lag the voltage by 90 degrees. Xc shrinks with frequency and makes current lead. In a series circuit they subtract, and they cancel at the resonant frequency.
Can I use this for safety or final design sign-off?
No. This calculator is for learning and design checks, not safety certification. Real inductors have winding resistance, core saturation and self-capacitance that change their behaviour, especially at high frequency.