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Inductance Calculator

Work out inductance instantly with clear inputs, formula shown and shareable results.

About Inductance Calculator

Inductance is mu0 x mur x N squared x A / l. The key feature is the N squared term: doubling the turns quadruples inductance. Core manufacturers publish this as an AL value in nH per turn squared, so L = AL x N squared for a given core.

Formula

Inductance

L = mu0 x mur x N^2 x A / l; AL = L / N^2

Worked example

With the default values below, Inductance Calculator returns Inductance of 24.43. Change any input above and every figure here is recalculated in your browser.

Inputs used

Number of turns
120 turns
Core cross-sectional area
1.2 cm²
Magnetic path length
8 cm
Relative permeability
900

Results

Inductance
24.43 mH
Magnetic reluctance
589,463 A/Wb
Core AL value
1,696.46 nH/turn²
Energy stored at 1 A
12.21 mJ

Step by step

  1. 1Values used
  2. 2Inductance
  3. 3Inductance= 24.43 mH
  4. 4Magnetic reluctance= 589,463 A/Wb
  5. 5Core AL value= 1,696.46 nH/turn²
  6. 6Energy stored at 1 A= 12.21 mJ

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

Why is inductance proportional to N squared?

One factor of N comes from the magnetising force produced, the other from the flux linkage seen by all the turns.

What is core saturation?

Above a certain flux density the permeability collapses, so inductance falls sharply with current. That is the real current limit of an inductor.

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