Inductance Calculator

L = μ₀N²A/ℓ for an ideal solenoid, or V = L(dI/dt) for the defining equation.

Inputs

Result

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How to use this calculator

  • Enter solenoid parameters: turns, cross-section area, and length.
  • Read inductance in H, mH, µH.

About this calculator

Inductance L resists changes in current. For an ideal solenoid: L = μ₀N²A/ℓ (where μ₀ = 4π × 10⁻⁷ T·m/A is vacuum permeability). The defining equation: V = L(dI/dt) — voltage across an inductor is proportional to rate of current change. Energy stored: E = ½LI².

Frequently asked

What does an inductor do in a circuit?+
Resists rapid changes in current. Stores energy in magnetic field. Used in filters (low-pass), transformers, and energy storage in switching power supplies.
Why does L scale with N²?+
Because both the magnetic field (B ∝ N) and the flux linkage per amp (∝ N) each contribute a factor of N.
What about iron-core inductors?+
Multiply L by the relative permeability μᵣ of the core material. Iron has μᵣ ~1000-5000 — same coil with iron core has 1000-5000× more inductance.
Series vs parallel inductors?+
Series: L = L₁ + L₂ (add). Parallel: 1/L = 1/L₁ + 1/L₂. Same rules as resistors.
Why mH or µH instead of H?+
A 1 H inductor is physically large. Practical circuits use mH (millihenrys) or µH (microhenrys). RF circuits go down to nH.

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