Productive ToolboxInductive Reactance Calculator
Calculate inductive reactance (XL) using frequency and inductance. Free online calculator with unit conversion and step-by-step explanations.
Inductive Reactance Calculator
Calculate inductive reactance (XL) using the formula XL = 2πfL. Get instant results with step-by-step explanations.
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Note: Inductive reactance (XL) increases as frequency increases. At DC (0 Hz), an inductor acts as a short circuit. At very high frequencies, it acts as an open circuit. This calculator uses the formula XL = 2πfL.
What Is an Inductive Reactance Calculator?
An inductive reactance calculator computes the opposition an inductor presents to alternating current using the formula XL = 2πfL. Enter frequency and inductance, and the calculator returns reactance in ohms with a full step-by-step derivation — no need to look up the 2π constant or convert units by hand.
Unlike plain resistance, inductive reactance depends directly on frequency, so the same inductor behaves completely differently at 60Hz mains frequency versus 1MHz RF — a distinction that's easy to compute wrong when switching between unit prefixes for frequency (Hz, kHz, MHz) and inductance (H, mH, µH, nH) in the same calculation. This tool handles all unit conversion automatically and shows every step of the derivation.
Built for electrical engineers designing filters and chokes, RF and radio hobbyists, electronics students learning AC circuit theory, and power electronics designerschecking impedance at a specific operating frequency. Includes six built-in frequency/inductance presets, full step-by-step working, and text export — free and entirely browser-based.
The Inductive Reactance Formula
Core Formula
Inductive Reactance (XL) = 2π × f × L
Example: 10mH inductor at 60Hz
XL = 2π × 60 × 0.01 = 3.77Ω
- f — signal frequency in hertz; reactance scales linearly with frequency
- L — inductance in henries; reactance scales linearly with inductance too
- 2π ≈ 6.2832 — the constant converting frequency (cycles/second) into angular frequency (radians/second)
- XL is zero at DC (f = 0) and increases without bound as frequency rises — the defining behavior of an inductor in an AC circuit
How to Use the Inductive Reactance Calculator
Step-by-Step Guide
- 1Enter frequency: Input the AC signal frequency, choosing Hz, kHz, or MHz as the unit.
- 2Enter inductance: Input the inductor's value, choosing H, mH, µH, or nH as the unit.
- 3Read the inductive reactance: The result updates instantly, showing XL in ohms using the formula XL = 2πfL.
- 4Review the step-by-step derivation: See the full calculation broken into each substitution step, useful for verification or learning the formula.
- 5Apply a preset (optional): Use one of six built-in presets spanning power-line frequencies (50/60Hz) through RF frequencies (1MHz) to explore how reactance scales.
- 6Save or export the result: Save the calculation to history, or export the full result with formula and steps as a text file.
What This Calculator Provides
- ✓Real-time calculation as you type
- ✓Full unit support: Hz/kHz/MHz, H/mH/µH/nH
- ✓Complete step-by-step derivation
- ✓Six built-in presets (50Hz to 1MHz)
- ✓Calculation history (saved locally)
- ✓Export calculation as a text file
- ✓100% browser-based — no data sent to server
- ✓No signup required
Real-World Use Cases
Mains Frequency Choke Sizing
An engineer designing a power-line filter needs a choke with at least 3Ω of reactance at 60Hz. Testing a 10mH inductor, the calculator returns XL = 3.77Ω — meeting the requirement — confirming the part before adding it to the filter design.
RF Choke Verification at 1MHz
An RF hobbyist wants to confirm a 10µH inductor provides enough isolation at 1MHz for a bias tee circuit. Using f = 1MHz and L = 10µH, the calculator returns XL = 62.8Ω — enough to isolate the RF signal from the DC bias supply for their intended application.
Audio Crossover Reactance Check
An audio hobbyist calculating a crossover inductor's behavior at a 2kHz crossover point tests a 2.5mH inductor. The calculator returns XL = 31.4Ω at 2kHz, which they compare against the speaker's impedance to estimate the crossover's -3dB point.
Current Draw Estimate for an Inductive Load
A technician wants to estimate current through a 100mH inductor connected across a 120V, 60Hz supply, ignoring winding resistance. The calculator returns XL = 37.7Ω, and dividing 120V by 37.7Ω gives an estimated current of 3.18A for this idealized reactive-only case.
LC Resonance Frequency Search
A student searching for the resonant frequency of an LC tank circuit with L = 100µH tests several candidate frequencies against a known 100pF capacitor's reactance. At 1.6MHz, XL for the 100µH inductor comes out close to the capacitor's XC at the same frequency, confirming they're near the circuit's resonant point.
Comparing Reactance Across Frequency Bands
An engineer wants to visualize how a fixed 1mH inductor behaves from mains frequency to RF. Testing 60Hz, 1kHz, 100kHz, and 1MHz in sequence, the calculator returns 0.377Ω, 6.28Ω, 628Ω, and 6,283Ω respectively — a span of four orders of magnitude that illustrates why the same component serves very different roles depending on operating frequency.
Tips & Common Mistakes
Pro Tips
- 💡Remember that reactance scales linearly with both frequency and inductance — doubling either one doubles XL, unlike inductance itself, which scales with turns squared in the underlying coil.
- 💡Use the built-in presets to quickly get a feel for typical XL magnitudes across frequency bands — mains chokes, audio crossovers, and RF chokes all operate in very different reactance ranges for very different component values.
- 💡When comparing an inductor's reactance to a capacitor's reactance for a filter or resonance calculation, always compute both at the same frequency — reactance is meaningless to compare unless the frequency is held constant.
- 💡For a quick real-world impedance check, remember that a real inductor's total impedance also includes its winding resistance (DCR) — XL alone describes only the ideal reactive component, not the full impedance magnitude.
- 💡When sizing a choke for a switching power supply, calculate XL at the actual switching frequency, not at the AC mains frequency — inductors intended for high-frequency ripple filtering behave very differently than 50/60Hz mains chokes.
Common Mistakes to Avoid
- ✕Forgetting the 2π factor and using XL = fL instead of XL = 2πfL. This understates reactance by a factor of roughly 6.28, a common shortcut error when working quickly by hand.
- ✕Mixing up frequency unit prefixes, especially Hz and kHz. Entering 60 intending Hz but leaving the unit on kHz overstates reactance by a factor of 1,000 — always confirm the unit dropdown matches your intended frequency.
- ✕Assuming XL alone represents a real inductor's total impedance. Real components also have winding resistance and, at high frequencies, parasitic capacitance — XL is only the ideal reactive component of a more complete impedance model.
- ✕Treating inductive reactance as if it behaved like resistance in terms of power dissipation. An ideal inductor's reactance opposes current without dissipating real power as heat — power is only dissipated in the winding's actual resistance, not in the reactance itself.
- ✕Using the wrong inductance value when a coil's inductance changes with frequency, as happens with ferrite-core inductors near saturation or self-resonance. This formula assumes a fixed, ideal inductance — real component datasheets often specify inductance at a particular test frequency for this reason.
Reactance by Frequency and Inductance
| Frequency | Inductance | Reactance (XL) |
|---|---|---|
| 50 Hz | 0.1 H | 31.4 Ω |
| 60 Hz | 0.05 H | 18.85 Ω |
| 1 kHz | 10 mH | 62.8 Ω |
| 10 kHz | 1 mH | 62.8 Ω |
| 100 kHz | 100 µH | 62.8 Ω |
| 1 MHz | 10 µH | 62.8 Ω |
* Calculated using XL = 2πfL. Note how the last four rows give equal reactance despite spanning three orders of magnitude in frequency and inductance.
Frequently Asked Questions
What is an inductive reactance calculator?
An inductive reactance calculator is a free online tool that computes the opposition an inductor presents to alternating current using the formula XL = 2πfL. Enter frequency and inductance, and the calculator returns reactance in ohms along with a full step-by-step derivation.
What is the formula for inductive reactance?
XL = 2πfL, where XL is inductive reactance in ohms, f is frequency in hertz, and L is inductance in henries. For example, a 10mH inductor at 60Hz gives XL = 2π × 60 × 0.01 = 3.77Ω, while the same inductor at 1kHz gives XL = 2π × 1,000 × 0.01 = 62.8Ω.
Why does inductive reactance increase with frequency?
An inductor opposes changes in current by generating a back-EMF proportional to the rate of change of current flowing through it. As frequency increases, current changes direction faster, so the back-EMF — and therefore the reactance — increases proportionally. This is why inductors are used to block or attenuate high-frequency signals while passing low-frequency ones.
What is the difference between inductive reactance and resistance?
Resistance dissipates electrical energy as heat and applies the same way at any frequency, including DC. Inductive reactance opposes changing current without dissipating energy as heat, exists only for AC or transient signals, is zero at DC, and scales linearly with frequency — making it a fundamentally different kind of opposition to current flow.
What is the inductive reactance at 0 Hz (DC)?
Zero. Since XL = 2πfL and f = 0 makes the entire expression zero, an ideal inductor presents no reactance to DC current — it behaves like a plain wire (aside from its winding resistance) once current has stabilized. This is why inductors are used as chokes to pass DC while blocking AC ripple or noise.
How do I calculate the resonant frequency of an LC circuit using reactance?
Resonance occurs when inductive reactance (XL) equals capacitive reactance (XC), at frequency f = 1 ÷ (2π√(LC)). Use this calculator to find XL at your suspected resonant frequency, and the companion capacitive reactance calculator to find XC at the same frequency — if they're equal, you've found resonance.
How does inductive reactance affect current in an AC circuit?
In a purely inductive AC circuit, current is limited by reactance similarly to how it's limited by resistance in a DC circuit: I = V ÷ XL. A 120V, 60Hz supply across a 100mH inductor (XL = 37.7Ω) draws about 3.18A — higher reactance from either higher frequency or higher inductance reduces the current for the same applied voltage.
Why do power transformers use different reactance considerations than RF chokes?
Power transformers operate at low, fixed frequencies (50 or 60Hz), so their windings need very high inductance to achieve meaningful reactance, requiring iron cores and many turns. RF chokes operate at much higher frequencies (kHz to MHz), so they need far less inductance to achieve the same or higher reactance, allowing smaller air-core or ferrite-core designs.
How is inductive reactance used in filter design?
In an LC low-pass filter, inductive reactance increases with frequency, progressively blocking higher-frequency signals while passing lower ones through with less opposition. Combined with a capacitor (whose reactance decreases with frequency), inductors and capacitors together create precise frequency-dependent filtering behavior used in power supplies, audio crossovers, and RF circuits.
Is my data private when using this calculator?
Yes. All calculations run entirely in your browser using JavaScript. Your frequency and inductance values are never transmitted to any server, stored in any database, or accessible to anyone other than you.
Who Uses This Inductive Reactance Calculator?
Electrical Engineers
Verify choke and filter inductor reactance at mains and switching frequencies during power electronics design.
RF & Radio Hobbyists
Calculate RF choke reactance and check isolation performance at radio frequencies.
Electronics Students
Learn how inductive reactance depends on frequency and verify AC circuit theory homework problems.
Audio Circuit Designers
Calculate crossover inductor reactance at target crossover frequencies for speaker networks.
Electronics Hobbyists
Estimate current-limiting behavior of inductive loads across different AC frequencies.
EMI/EMC Engineers
Confirm inductive filter components provide sufficient reactance at target noise frequencies.