STL to STEP Converter

Turn a triangle mesh into a real CAD solid. Our engine recognizes planes and cylinders and rebuilds them as true analytic CAD surfaces — a plate with two holes converts to exactly 8 faces, same as native CAD, not 500 triangles. Every job reports the method used, face count and volume accuracy.

Analytic feature recognitionHoles become true cylindersQuality metrics on every jobFree ≤25 MB

Why STL to STEP is hard (and what we do about it)

An STL is just triangles — no surfaces, no features, no topology. Most free converters wrap every triangle as a tiny CAD face and call it done: the file opens, but with 50,000 faces your CAD grinds and editing is hopeless.

StlWiz reconstructs geometry in three tiers, best first: analytic recognition detects planar and cylindrical regions and rebuilds them as true CAD surfaces — holes become real cylinders with exact circular edges, so a machined plate converts to the same handful of faces native CAD would produce; coplanar merging handles what recognition can't; a faceted fallback guarantees you always get a valid solid. Every result is verified as a closed solid with volume checked against your mesh — if quality gates fail at one tier, we drop to the next instead of shipping garbage. Benchmarks: a plate with two holes converts to exactly 8 faces (native-CAD parity); volume preserved to 99.98%.

Heads-up on expectations: organic sculpts fundamentally can't become tidy parametric CAD — that's true of every tool. For mechanical parts, this is as clean as web converters get.

Frequently asked questions

How do I convert STL to STEP for free?
Drop your STL above, click Convert, download the STEP. Files up to 25 MB are free (10/day); meshes above ~15,000 faces are auto-simplified for tractability — the metrics line shows exactly what happened.
Will the STEP file be editable in Fusion 360 or SolidWorks?
It imports as a solid body you can measure, section, boolean and machine. Face-level editing depends on your part: merged planar faces edit nicely; curved regions remain faceted (a fundamental limit of mesh sources — no converter produces true parametric features from STL).
Why is my converted STEP file large?
STEP stores every face explicitly. Our coplanar merging reduces face count substantially versus naive converters, and auto-simplification keeps big meshes tractable. If you need higher fidelity, large-file credits raise the face budget to 50,000.
Is this converter free?
Yes — up to 10 conversions a day and files up to 25 MB, no account needed. Larger files (up to 60 MB) and high-detail STEP output use credits ($9 for 20). Everything runs server-side on real geometry kernels, and failed jobs auto-refund.
What happens to my files?
Files are uploaded only to run your conversion and stored briefly so you can download the result. We don't share them, mine them or train on them. See our privacy policy.