About the Inductive Reactance Calculator
A coil lets direct current pass freely but resists alternating current, and it resists it more as the frequency rises. That opposition is called inductive reactance, written XL, and it is measured in ohms. This calculator takes the inductance and the frequency, gives XL, and, if you also enter a voltage, the current that would flow. Type the inductance and the frequency, and optionally the voltage and the inductive reactance appears at once, with a few related figures underneath, and you can copy the result with one tap. The sums run in your browser, so nothing you enter is uploaded.
Updated October 2026
How to use the Inductive Reactance Calculator
- 1Enter the inductance and the frequency, and optionally the voltage.
- 2Pick the units or options from the menus if the inductive reactance tool offers them.
- 3Read the inductive reactance in the large result box.
- 4Look at the extra rows for related figures.
- 5Press Copy result to keep the answer.
When you need the inductive reactance
Designers use XL to choose chokes that block radio-frequency noise on a power line, to size the coils in a low-pass filter, and to predict how much current a motor winding or a transformer coil draws on mains. The figure also shows why coils make poor DC blockers but good AC blockers.
Reactance is not the same as resistance: it does not turn power into heat. The voltage across an ideal inductor leads the current by 90 degrees, so the power is stored and returned each cycle. Real coils also have winding resistance, which adds a little.
How the inductive reactance is worked out
XL = 2π × frequency × inductance. At 0 Hz (direct current) the reactance is 0. A 10 millihenry coil at 1 kHz has a reactance of 2π × 1,000 × 0.01 = 62.83 Ω. At 50 Hz the same coil has only 3.14 Ω, and at 100 kHz it reaches 6.28 kΩ. With 12 V across it at 1 kHz the current would be about 191 mA.
Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.
- Any frequency unit
- Optional current at a given voltage
- Angular frequency shown
Mistakes to avoid with inductive reactance
Do not mix units: 10 mH is 0.01 H, not 10 H. The tool converts for you. Also, the formula uses frequency in hertz and gives ohms only for a pure inductor. A real coil near its self-resonant frequency behaves differently because of its internal capacitance.
On phone and computer
On a phone, type into the boxes one after another and read the inductive reactance underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the inductive reactance move. The inductive reactance calculator works the same on both. Compare with Capacitive Reactance Calculator, choose a part with Inductor Calculator, check the current with Ohm's Law Calculator, and change the frequency unit with Frequency Converter.
Features
- Rises with frequency
- Not the same as resistance
- Convert mH to H
- Clear messages when the inductive reactance inputs make no sense
- Copy the result with one tap
- Private: nothing is uploaded
Frequently asked questions
How do I calculate inductive reactance?
XL = 2π × frequency × inductance. At 0 Hz (direct current) the reactance is 0. A 10 millihenry coil at 1 kHz has a reactance of 2π × 1,000 × 0.01 = 62.83 Ω. At 50 Hz the same coil has only 3.14 Ω, and at 100 kHz it reaches 6.28 kΩ. With 12 V across it at 1 kHz the current would be about 191 mA.
What is the formula for inductive reactance?
XL = 2π × frequency × inductance. At 0 Hz (direct current) the reactance is 0. The inductive reactance calculator applies it exactly and rounds only the displayed answer to six significant figures.
Does reactance depend on frequency?
Yes, directly. Double the frequency and XL doubles.
What is the phase between voltage and current?
In an ideal inductor the current lags the voltage by 90 degrees.
What happens at DC?
The frequency is 0, so XL is 0 and only the wire resistance limits the current.
Is this inductive reactance calculator free and private?
Yes. It is free, needs no account and runs in your browser, so the numbers you type are not uploaded or stored.