This toroid inductance calculator finds the inductance of a toroidal coil from the number of turns and the core geometry, and reports the AL value per turn squared. Enter the values above.
Formula
L = μ₀μr × N² × h × ln(OD ÷ ID) ÷ (2π)
- h — core height, OD/ID — outer/inner diameter, μr — relative permeability
Example
μr = 100, N = 10, h = 5 mm, OD = 20 mm, ID = 10 mm: L = 6.93 µH (AL ≈ 69 nH/turn²).
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Frequently Asked Questions
How do I calculate toroid inductance?
Use L = mu0 mur N squared h ln(OD/ID) / 2pi, or multiply the core’s AL value by turns squared.
What is the AL value?
It is the inductance per turn squared for a specific core, so L equals AL times N squared.
Why use a toroid core?
Toroids confine the magnetic field inside the core, giving high inductance with low radiation and coupling.