STL to STEP

STL to STEP Converter

Turn a triangle mesh into a real STEP solid your CAD package can open, measure and machine from. Runs entirely in your browser — your geometry is never uploaded anywhere.

Read this first: the result is a faceted solid, not a parametric model.

Every triangle in your mesh becomes a flat face in the STEP file. You get a genuine, watertight B-rep solid — CAD will open it, measure it, and CAM will machine it. What you will not get is a parametric model: no analytic cylinders or fillets, no sketches, no feature tree, and curved surfaces stay as many small flat facets. That information was destroyed when the model was exported to STL and no converter can recover it. Anyone claiming otherwise is selling you something.

Convert STL to STEP

Upload an STL file, choose the units it was modelled in, and download a STEP solid.

Drop an STL file here or click to browse

Supports ASCII and Binary STL formats

Private by Design

Conversion happens in your browser. Your part never leaves your machine — no upload, no server copy, nothing to leak under an NDA.

A Real Closed Solid

Output is an ISO 10303-21 faceted B-rep in a closed shell — not a point cloud or a surface soup. CAD reads it as one solid body.

Honest About Limits

We tell you up front that faceted is not parametric, so you know what you are getting before you send it to a client or a machinist.

How STL to STEP Conversion Actually Works

An STL file is nothing but a bag of triangles. A STEP file describes boundary representation geometry — faces, edges and vertices with real mathematical surfaces behind them. Converting mesh to STEP means wrapping each triangle as a planar face and stitching them into a closed shell. The result is a legitimate solid, which is why CAD and CAM accept it.

What You Get

  • A watertight solid body that CAD opens as one part, not a collection of surfaces
  • Accurate dimensions — vertex positions are preserved exactly, so measurements match the mesh
  • A machinable deliverable that CAM software can toolpath against
  • A STEP file to hand a client when the spec says "STEP only" and all you have is a mesh

What You Do Not Get

  • Parametric features: no sketches, extrudes, or feature tree to edit
  • Analytic surfaces: a cylinder stays as flat facets, not a true cylindrical face, so you cannot select "the hole" and change its diameter
  • Small file sizes: faceted STEP runs roughly 290 bytes per triangle, so a 100,000 triangle mesh lands near 29 MB
  • Clean fillets: curved blends arrive as many narrow flat faces

When This Is the Right Tool

  • A client or shop demands STEP and the mesh is all that exists
  • Import into CAD as a reference body to build new parametric geometry around
  • Measuring and inspection where exact vertex positions matter more than editability
  • Scanned or sculpted parts that were never parametric to begin with

When You Need Something Else

If you need to edit dimensions parametrically, no mesh-to-STEP converter will help — the design intent is gone. Your options are remodelling the part in CAD from measurements, or using reverse-engineering software that fits analytic surfaces to a scan, which is a supervised, manual process. Any free tool promising a fully parametric model from an STL is misrepresenting what it does.

Tips for a Clean Result

  • Reduce very dense meshes before converting — face count drives both file size and CAD performance
  • Repair non-manifold geometry first so the shell closes properly; try the Manifold Checker
  • Confirm your units before converting — STL stores no unit, so a millimetre part can arrive 25.4x wrong
  • Going the other way? Use the STEP to STL converter for print-ready meshes