Calculator of inductance of a straight round magnetic wire

Stan Zurek, Calculator of inductance of a straight round magnetic wire, Encyclopedia Magnetica,
https://www.e-magnetica.pl/doku.php/calculator/inductance_of_straight_round_magnetic_wire, {accessed: 2025-03-14}
See more: Calculators of inductance
Definition of the dimensions of a straight round wire

Inductance of a straight wire or conductor made from magnetic material with round (circular) cross-section can be calculated with the the equation as specified below.

Wire diameter d = 2·r =      

Wire length l =      

Relative permeability of the wire μr = (unitless)

      

LDC = Rosa, eq. (1)

Note: Several assumptions are made for all these equations: 1) The return path is not considered so the total inductance of the complete circuit can be significantly different. 2) The length of the wire is assumed to be significantly longer than it radius (r « l), otherwise the errors might be excessive. 3) The surrounding medium is assumed to be non-magnetic (μr = 1). 4) The current is uniformly distributed inside the wire (no skin effect). 5) The equations were converted here to be consistent with SI units.

Inductance of a straight round magnetic wire or conductor
Sources: [1] Edward B. Rosa, The self and mutual inductance of linear conductors, Department of Commerce and Labor, Bulletin of the Bureau of Standards, Volume 4, 1907-8, Washington, 1908,
[2] F.W. Grover, Inductance Calculations: Working Formulas and Tables, ISA, New York, 1982, ISBN 0876645570
(1)
[1] Rosa, eq. (11), p. 305
and [2] Grover, eq. (8), p. 35
$$ L = \frac{μ_0 ⋅ l}{2⋅π}⋅\left( ln \left( \frac{2⋅l}{r} \right) - 1 + \frac{μ_r}{4} \right) $$ (H)
where: $μ_0$ - magnetic permeability of vacuum (H/m), $l$ - wire length (m), $r$ - wire radius (m), $μ_r$ - relative magnetic permeability of the wire (unitless)
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