Toroid Inductor

Powdered-iron and ferrite toroid cores are specified by an inductance factor A_L, so the inductance is simply A_L·N². Enter A_L and a target inductance to get the required turns (and the inductance the nearest whole turn actually gives), or enter a turn count to get the inductance. An optional flux-density check flags core saturation at a given drive.

Equations & Parameters ▸

\(L=A_L\,N^2 \qquad N=\sqrt{\dfrac{L}{A_L}} \qquad B_{peak}=\dfrac{V_{rms}\sqrt2}{2\pi f\,N\,A_e}\)

A_L	Core inductance factor (nH/N²), from the core datasheet.
L	Target inductance (µH). Leave blank to compute L from a given N.
N	Number of turns. Leave blank to compute from a target L.
V_rms, f, A_e	Optional: applied RMS voltage, frequency (MHz), and core effective area (mm²) for the peak flux density.

Reference: Amidon / Micrometals / Fair-Rite core datasheets; ARRL Handbook, toroidal inductors.

Inputs

A_L value

nH/N²

From datasheet

Target L (or N)

µH

Desired

Turns N (or L)

Wound

V_rms (opt)

For flux

Frequency (opt)

MHz

For flux

A_e (opt)

mm²

Core area

Results

Turns / inductance

Exact turns—

Rounded turns—

Inductance at rounded N—

Flux

Peak flux density B—

Diagram

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