FEMM vs COMSOL for coils.
A free 2D finite element program against a commercial 3D multiphysics suite. For many coils and inductors FEMM is all you need; the question is when the geometry stops being two-dimensional.
Last reviewed: October 2026
Two very different tools
FEMM (Finite Element Method Magnetics), written by David Meeker, is a free Windows program that solves low-frequency magnetic, electrostatic, heat-flow and current-flow problems on 2D planar and axisymmetric domains. It is distributed under the Aladdin Free Public Licence, and its last stable release, 4.2, is from 2019. It is small, quick to learn and a staple of electromagnetics teaching.
COMSOL Multiphysics is a commercial general-purpose finite element suite. With the AC/DC Module it solves magnetic problems in 2D, axisymmetric and full 3D, in stationary, frequency-domain and time-dependent studies, and couples them to heat transfer, mechanics and circuits. It costs far more and asks more of the user, but it has no symmetry limits.
When 2D axisymmetric is enough
Any coil that is a body of revolution around one axis can be modelled as an axisymmetric slice: a solenoid, a pot-core inductor, a toroid's cross-section, a circular spiral, or two circular coils on the same axis at any gap. FEMM solves these in seconds to minutes and reports flux linkage, inductance and losses for each circuit, so you get self- and mutual inductance from one solve. For coaxial wireless power coils this is accurate and free.
Symmetry breaks once coils move sideways, tilt, become square, or sit near a rectangular ferrite plate or a phone chassis. A lateral offset between transmitter and receiver is exactly the case wireless charging designers care about, and FEMM cannot represent it. That is where COMSOL, or another 3D tool, becomes necessary.
FEMM vs COMSOL vs AirInduct Sim
How the two FEM tools compare for coils and inductors, with AirInduct Sim alongside for 3D air-core work.
| Criterion | FEMM | COMSOL Multiphysics | AirInduct Sim |
|---|---|---|---|
| Solver method | FEM | FEM (AC/DC Module for magnetics) | Closed-form Biot–Savart + Neumann mutual inductance, no mesh |
| Geometry | 2D planar and axisymmetric only | 2D, axisymmetric and full 3D | 3D coil geometry and fields |
| Magnetic problem types | Magnetostatic and time-harmonic; no transient | Stationary, frequency-domain and time-dependent | Air-core magnetostatic coupling |
| Eddy currents and AC loss | Yes, time-harmonic, in 2D | Yes, in 2D and 3D, including skin and proximity effects | Not modelled |
| Lateral misalignment | Not possible: offset breaks axial symmetry | Yes, in a 3D model | Yes, sweep offset and gap directly |
| Ferrite and cores | Yes, linear and nonlinear | Yes, linear and nonlinear | Not modelled — air-core only |
| Scripting | Built-in Lua; pyFEMM for Python; MATLAB/Octave | COMSOL API for Java, LiveLink for MATLAB | AI Copilot and MCP server drive the real solver |
| Install / platform | Desktop, Windows (Wine on Linux) | Desktop, Windows, macOS and Linux | Browser, plus iOS and Android apps |
| Licence / cost | Free, Aladdin Free Public Licence | Commercial, quote-based; AC/DC Module is an add-on | Free plan + Pro subscription |
| Learning curve | Hours: small, focused interface | Weeks: broad, general-purpose interface | Minutes: topology presets |
| Time to first result | Minutes for a 2D model | Minutes to hours | Seconds |
| WPT outputs (L, M, k) | L and M from circuit flux linkage, coaxial coils only | Inductance matrix; you derive k | L, M and k on every run |
Competitor details are taken from public vendor pages and documentation, last reviewed October 2026. Product names are trademarks of their respective owners and are used only to identify them. AirInduct is not affiliated with, endorsed by or sponsored by any of these vendors.
Eddy currents, scripting and cost
Both tools handle AC. FEMM's time-harmonic magnetics solves eddy currents at a single frequency, which covers skin effect in solid conductors and loss in nearby metal for symmetric geometry; it has no transient solver. COMSOL adds 3D frequency-domain and time-dependent studies, so it can follow a switching waveform or a nonlinear core through time.
Automation is a real strength of FEMM. Lua is built in, pyFEMM drives it from Python, and MATLAB and Octave interfaces exist, so parameter sweeps over turns and spacing are a short script. COMSOL offers the COMSOL API for Java, LiveLink for MATLAB and built-in parametric sweeps, with more power and more setup.
Cost is simple: FEMM is free, and COMSOL is a commercial, quote-based licence with the AC/DC Module as an add-on. For more detail, see our FEMM alternative and COMSOL alternative pages.
Where AirInduct Sim fits
AirInduct Sim sits between the two for one job: 3D air-core wireless power coils. It computes fields with closed-form Biot–Savart and coupling with the Neumann integral, so it has the 3D misalignment that FEMM lacks, solves in seconds, and needs no install or COMSOL licence. Eight topology presets, including Helmholtz pairs and descending-turn planar spirals, report L, M and k on every run.
It does not model ferrite, cores or eddy currents, so it is not an inductor-design tool in the way FEMM and COMSOL are. It is free to start: the free plan covers the Helmholtz topology with 3 simulations a month, and AirInduct Pro unlocks every topology, the AI Copilot and unlimited runs (see pricing). Try a misalignment sweep, or compare more tools in the best WPT simulation software.
Which should I use?
Use FEMM when your coil or inductor is axisymmetric or planar, COMSOL when it is not, and AirInduct Sim when you need 3D air-core coupling fast without a COMSOL licence. FEMM is free, quick to learn and accurate for solenoids, pot cores and coaxial coil pairs, and its Lua and Python scripting make sweeps easy. It cannot model lateral misalignment, square pads or nonsymmetric shields, and it has no transient solver. COMSOL removes those limits with full 3D, time-dependent studies and multiphysics coupling, at the cost of a commercial licence and a steeper learning curve. For wireless power work, a sensible path is FEMM for symmetric checks and teaching, AirInduct Sim for 3D offset and gap sweeps on air-core coils, and COMSOL once ferrite, shielding or thermal effects must be modelled in 3D. If you already hold a COMSOL licence, its 2D axisymmetric mode replaces FEMM too.
Compare with other tools
See all 20 AirInduct Sim alternatives and comparisons →Go 3D on air-core coils, in seconds.
Frequently asked questions
Is FEMM accurate enough for inductor design?
Yes, for geometries that really are axisymmetric or planar: solenoids, pot cores, coaxial coil pairs and many inductor cross-sections. FEMM is widely used in teaching and research and converges well when the mesh near conductors is refined.
Can FEMM simulate two misaligned wireless charging coils?
No. FEMM solves 2D planar or axisymmetric problems, and a lateral offset between two coils breaks axial symmetry. You need a 3D tool such as COMSOL, or AirInduct Sim for air-core coils.
Does FEMM run on Mac or Linux?
FEMM is a Windows program. Users run it on Linux and macOS through Wine, and the FEMM site documents Linux use, but it is not a native port. COMSOL runs natively on all three.
Should I learn FEMM before COMSOL?
It is a good start. FEMM teaches meshing, boundary conditions and flux linkage with little overhead, and those ideas carry straight into COMSOL. Moving to COMSOL is mainly about learning 3D modelling and its larger interface.