Case 1
- Frequency
- 50Hz
- Inductance
- 0.1H
31.415927Ω
Open with these valuesInductive Reactance Calculator
31.415927Ω
Result: 31.415927 ΩA coil opposes alternating current more and more as the frequency rises: a 100 mH choke is 31.4 Ω on 50 Hz mains and 628 Ω at 1 kHz. At direct current the reactance is zero and only the wire's own resistance remains.
The numbers at a glance
Held fixed: Frequency 50.00 Hz.
| Inductance (H) | Result (Ω) |
|---|---|
| 0.025000 | 7.853982 |
| 0.050000 | 15.707963 |
| 0.075000 | 23.561945 |
| 0.100000Your value | 31.415927 |
| 0.125000 | 39.269908 |
| 0.150000 | 47.123890 |
| 0.175000 | 54.977871 |
| 0.200000 | 62.831853 |
Worked examples
Case 2
- Frequency
- 1000Hz
- Inductance
- 0.01H
62.831853Ω
Open with these valuesCase 3
- Frequency
- 400Hz
- Inductance
- 0.002H
5.026548Ω
Open with these valuesHow it's calculated
XL = 2 × π × f × L
- StepEnter the frequency of the signal in hertz.
- StepEnter the inductance in henries — 100 mH is 0.1.
- ResultRead the reactance in ohms; it rises with both inputs.
Reference table
| Frequency, inductance | What that is | Reactance |
|---|---|---|
| 400, 0.002 | 2 mH at 400 Hz aircraft power | 5.026548 |
| 50, 0.1 | 100 mH choke on 50 Hz mains | 31.415927 |
| 60, 0.1 | The same choke on 60 Hz mains | 37.699112 |
| 1000, 0.01 | 10 mH at 1 kHz | 62.831853 |
| 60, 0.5 | 500 mH transformer winding | 188.495559 |
Questions
What is inductive reactance?
The opposition a coil offers to alternating current, measured in ohms. It stores energy in a magnetic field and returns it each half cycle instead of turning it into heat.
Why does it rise with frequency?
A coil resists any change in the current through it, and a faster alternation is a faster change. At direct current nothing changes, so the reactance is zero.
Can I add it to a resistance in the same circuit?
Not directly. The coil's current lags the voltage by a quarter cycle, so the two combine as Z = √(R² + XL²).
Where do I get the inductance from?
From the part's data sheet, from a meter, or — for a home-wound air-core coil — from the coil inductance calculator linked below.
Sources and last check
Information, not professional advice.