Inductance Calculator
Inductance measures the tendency of an electrical conductor to oppose changes in electric current by generating a proportional opposing electromotive force (EMF = -L · di/dt) via Faraday's Law of Induction. For a cylindrical solenoid or helical inductor coil, inductance scales quadratically with turn count and permeability (L = μ₀·μᵣ·N²·A / l). This calculator evaluates coil inductance, inductive reactance, and magnetic energy storage.
Total count of complete helical wire loops wound on the coil form
Inner cylindrical diameter of the coil in millimetres (mm)
Total axial winding length from end to end in millimetres (mm)
Magnetic core multiplier (1 for Air/Vacuum, ~600 for Ferrite, ~5,000 for Silicon Steel)
Operating current flowing through the coil in Amperes (A)
Operating AC signal frequency in Hertz (Hz) for inductive reactance calculation
Self-inductance of the solenoid in microhenrys (1 µH = 10⁻⁶ H)
How to Use This Calculator
- Enter the number of wire turns wound onto the coil.
- Input the inside coil diameter and overall axial length in millimetres.
- Specify core relative permeability (1 for air core, higher for ferrite/iron cores).
- Set current and signal frequency to view stored magnetic energy and inductive reactance.
Formula & Calculation Methodology
Self-inductance (L) scales quadratically with turn count N and cross-sectional area A (π·r²), and inversely with coil length l. Stored magnetic energy is half inductance times current squared. Inductive reactance increases linearly with AC frequency.
Worked Example
Air-core solenoid of 100 turns, 20 mm diameter, 50 mm length at 2A current and 1 kHz
Frequently Asked Questions
Why does winding more turns increase inductance quadratically (N²)?↓
Adding turns increases both the total magnetic flux generated per Ampere and the number of wire loops that link that magnetic flux, multiplying total self-linkage by N × N = N².
What is the benefit of a ferromagnetic core in an inductor?↓
Ferromagnetic materials like iron and ferrite align their magnetic domains with the coil's field, boosting effective core permeability (μᵣ) by hundreds or thousands of times, dramatically reducing the coil size needed for a target inductance.
Why do inductors block high frequencies while passing low frequencies?↓
Inductive reactance (XL = 2πfL) is directly proportional to frequency. At DC (f = 0), reactance is zero (pure wire). As frequency escalates into megahertz, back-EMF creates massive impedance against current flow.
What limitation applies to short stubby coils where length is less than diameter?↓
The standard solenoid equation assumes a long solenoid (length l ≫ diameter d) with uniform interior magnetic fields. For short coils, magnetic field lines bulge outward at the ends, requiring empirical Nagaoka or Wheeler correction factors.
Related Calculators
Source Citation & Disclaimer
Informational tool only; not licensed tax, legal, or financial advice.