How this calculator works
A long solenoid produces a nearly uniform internal magnetic field proportional to turns per unit length and current. The right-hand rule sets the direction: curling fingers with winding current points the thumb along the internal field. Core permeability scales the ideal field only while the core behaves linearly. This model describes the interior well away from the ends, not the external field or a short coil.
Formula
B = mu0 mur N I/l; I = Bl/(mu0 mur N); N = Bl/(mu0 mur I).
Worked example
A 100-turn air-core solenoid 1 m long carrying 2 A produces about 0.251327 mT. For the same coil, 0.125664 mT requires 1 A.
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Frequently asked questions
Why is there no radius input?
The ideal infinitely long solenoid field depends on turns per length, not radius. Finite-coil corrections do depend on radius.
Can I reverse the current?
Yes. Reversing signed current reverses signed field in this linear model.
Does this describe the field at the end?
No. The interior approximation is inaccurate near ends and outside the winding.