Inductor Calculator – Inductance and Inductive Reactance Calculator
Analyze inductor behavior in circuits with our inductor calculator. Compute inductance, inductive reactance (XL), and impedance for AC circuit design and electronics.
L = (μ₀ × μᵣ × N² × A) / l
How to Use This Inductor Calculator
Select your calculation type
Choose between inductance from physical parameters, inductive reactance, or total impedance.
Enter the required values
Input the parameters for your selected calculation. For inductance, enter turns, area, length, and permeability.
View your results
The calculator displays results with appropriate units (H, mH, µH, nH for inductance; Ω, kΩ, MΩ for reactance).
Common Core Materials and Permeability
| Core Material | Relative Permeability (µr) | Typical Applications |
|---|---|---|
| Air (vacuum) | 1 | RF circuits, high-frequency applications |
| Ferrite (Mn-Zn) | 1,000 - 15,000 | Power supplies, EMI suppression |
| Ferrite (Ni-Zn) | 100 - 1,000 | High-frequency transformers, RF |
| Iron powder | 2 - 100 | RF inductors, tuned circuits |
| Silicon steel | 4,000 - 9,000 | Power transformers, low-frequency |
| Permalloy | 8,000 - 100,000 | Sensitive instruments, magnetic shields |
| Amorphous metal | 10,000 - 50,000 | High-efficiency transformers |
Permeability values are approximate and vary by specific alloy composition and manufacturing process.
Understanding Inductor Calculations
What Is Inductance?
Inductance measures a coil's ability to store energy in a magnetic field. When current flows through a coil, it creates a magnetic field. Changing current induces a voltage that opposes the change. This property is measured in henries (H). Most inductors range from nanohenries to millihenries.
The Inductance Formula
L = (µ₀ × µᵣ × N² × A) / l. N is the number of turns — more turns mean more inductance. A is the core cross-sectional area. l is the magnetic path length. µ₀ is the permeability of free space (4π × 10⁻⁷ H/m). µᵣ is the relative permeability of the core material.
Inductive Reactance Explained
Inductive reactance (X_L) is the opposition an inductor presents to AC current. X_L = 2πfL, where f is frequency and L is inductance. Unlike resistance, reactance changes with frequency. At DC (0 Hz), an ideal inductor has zero reactance. At high frequencies, reactance can be very large.
Impedance in RL Circuits
Real inductors have both inductance and wire resistance. Total impedance Z = √(R² + X_L²). This combines resistance and reactance as a vector sum. Impedance determines how much current flows for a given AC voltage. Phase angle between voltage and current depends on the R/X_L ratio.
Tips for Inductor Design and Selection
Choose core material for your frequency
Ferrite works well for high frequencies. Iron powder suits RF applications. Silicon steel is best for 50/60 Hz power applications.
Watch for core saturation
Every core has a maximum flux density. Exceeding it causes saturation, where inductance drops sharply. Check the core's Bsat rating and ensure your peak current stays within limits.
Consider wire gauge for current handling
Thicker wire handles more current with less resistance. Use a wire gauge chart to match your expected current. For high-frequency applications, consider Litz wire to reduce skin effect losses.
Account for parasitic effects
Real inductors have inter-winding capacitance and series resistance. At high frequencies, self-resonance can make an inductor behave like a capacitor. Check the self-resonant frequency in datasheets.
Frequently Asked Questions
How do I increase inductance?
Add more turns — inductance increases with the square of turns. Use a core with higher permeability. Increase the cross-sectional area of the core. Decrease the magnetic path length. Adding a ferromagnetic core can increase inductance by orders of magnitude compared to air.
What is the difference between inductance and reactance?
Inductance (L) is a physical property of the coil, measured in henries. It does not change with frequency. Reactance (X_L) is the opposition to AC current, measured in ohms. Reactance depends on both inductance and frequency: X_L = 2πfL.
Why does an inductor block high frequencies?
Inductive reactance increases with frequency. At high frequencies, X_L becomes very large, limiting current flow. This makes inductors useful as low-pass filters — they pass DC and low frequencies while blocking high frequencies.
What is the Q factor of an inductor?
Q factor (quality factor) is the ratio of reactance to resistance: Q = X_L / R. Higher Q means lower losses and better performance in tuned circuits. Air-core inductors typically have higher Q than ferrite-core inductors at RF frequencies.
How do I calculate inductance for a toroidal core?
Use the same formula: L = (µ₀ × µᵣ × N² × A) / l. For a toroid, A is the cross-sectional area of the core ring. l is the mean magnetic path length (approximately π × mean diameter). Many toroid datasheets provide an AL value for easier calculation.
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