STL to STEP Converter

Drop an STL (or OBJ) and download a STEP file — converted entirely in your browser, never uploaded to a server. One honest caveat most converters bury: an STL is a triangle mesh, so the STEP you get is a faceted solid for manufacturing handoff, not an editable parametric model.

Drop an STL or OBJ file here

Your file is processed in your browser — never uploaded.

Open the editor →

What you get — and what you don't

This converts your mesh into a valid STEP (ISO 10303-21) solid: every triangle becomes a planar face, welded into a B-rep — a closed solid when your mesh is watertight, an open surface model when it isn't — that opens in Fusion 360, SolidWorks, FreeCAD, and most CAM and quoting tools.

What it is not is a reconstruction. An STL stores only triangles — no curves, no holes, no design history. There is no way to recover those from a mesh — no free tool can, and no paid one reliably can either. So the STEP you download is a faceted solid: a cylinder comes back as many flat strips, not a true cylinder, and you can't grab a face and change a dimension. If you need an editable parametric model, this — and every other STL→STEP converter — can't give you one. Here's why, in plain terms.

Use this when you need to hand geometry to someone downstream:

  • Getting a CNC machining quote or a 3D-printing-service order that asks for STEP.
  • Sending a part to a machine shop or mould maker to inspect wall thickness, draft, and fit.
  • Importing a mesh into CAD as a fixed reference body to build around.

Don't use this when you expected to edit the result like native CAD. You won't be able to, and that's a property of the STL format, not this tool.

Your file never leaves your browser

Most "free online" converters upload your STL to their servers, run the conversion there, and keep the output on their servers for a while afterward. For a client's part or anything proprietary, that's a real exposure.

Cadre converts locally. The geometry kernel is compiled to WebAssembly and runs inside this tab — your file is read, converted, and handed back as a download, and your geometry never goes to a server. No upload, no account, no retention, no watermark.

How it works

Cadre is a browser-based CAD editor whose Rust geometry kernel runs client-side via WebAssembly — the same kernel that powers the modeller does the conversion here in an isolated, in-tab session. Drop a file and you get a STEP back almost instantly for typical print-sized models; very large scans take longer because everything runs on your machine, not a server farm.

FAQ

Is the converted STEP file editable in SolidWorks or Fusion 360?

No — and no STL-to-STEP converter can make it so. An STL is a triangle mesh with no curves, holes, or design history, so the STEP you get is a faceted solid: a fixed reference body, not a parametric model you can grab and re-dimension. Recovering an editable model from a mesh is a manual reverse-engineering job, not a conversion.

Does my file get uploaded anywhere?

No. The conversion runs locally in your browser via WebAssembly. Your STL is never uploaded to a server, never stored, and never retained — unlike most online converters, which upload your file and keep the output for a while.

Is it free?

Yes — converting STL to STEP is free, with no account, no upload, and no watermark on the output.

Can a CNC shop or 3D-printing service use this STEP file?

Yes. A faceted STEP is a valid geometry container that machine shops, quoting portals, and CAM software can ingest for quoting, inspection (wall thickness, draft, fit), and visualization. Just know it carries the triangle facets, not the clean analytical surfaces a model authored natively in CAD would have.

Why can't an STL be converted to a clean, editable STEP?

An STL only stores unstructured triangles — it threw away the curves, features, and dimensions when it was exported. There is no information left to rebuild them from, so even high-end CAD (SolidWorks, CATIA, NX) cannot reliably auto-convert a mesh into an editable solid. Any tool claiming otherwise is either wrapping the triangles unchanged or doing slow, lossy surface-fitting.

What's the difference between this and a STEP file exported from CAD?

A STEP authored in CAD stores exact mathematical surfaces — a cylinder is a cylinder, a hole is a hole. A STEP converted from an STL stores the mesh's flat triangles instead, so curved regions are faceted and faces can't be selected as design features. Both are valid STEP files; only the CAD-authored one is truly editable.

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