STEP to STL

STEP to STL Converter

Turn CAD parts into print-ready meshes. Real B-rep tessellation via the OpenCascade kernel, so holes and fillets come out round instead of chunky — and nothing ever leaves your browser.

Convert STEP to STL

Upload a .step or .stp file, choose how finely to tessellate curves, then download a printable STL.

Drop a STEP file here or click to browse

Supports .step and .stp (AP203, AP214, AP242)

True Curve Tessellation

Powered by OpenCascade, the same kernel behind FreeCAD. Cylinders, splines and fillets are meshed from their real mathematics, not approximated.

Nothing Uploaded

The CAD kernel runs inside your browser as WebAssembly. Confidential parts stay on your machine.

You Control Resolution

Dial the chord tolerance for a fast draft or a smooth production mesh, and see the triangle count before you download.

How to Convert STEP Files to STL

STEP files describe parts with exact mathematical surfaces. Slicers cannot read them — they need triangles. Converting means tessellating: sampling those surfaces finely enough that the mesh matches the true shape within a tolerance you choose. Set that tolerance too loose and round holes print as polygons; too tight and you get an enormous file for no visible gain.

Choosing a Mesh Quality

  • Draft: quick check of fit and proportion; facets are visible on curved surfaces
  • Standard: the right choice for most FDM prints at 0.2 mm layers
  • Fine: resin prints, visible cosmetic curves, or large parts where facets would show
  • Custom: type an exact chord tolerance if your shop has a required value

Why Tolerance Is Relative

The tolerance here is a fraction of the part's bounding box rather than a fixed millimetre value. That way one setting behaves sensibly whether you are converting a 10 mm bracket or a one metre enclosure, instead of producing millions of triangles on big parts.

Common Problems

  • "No solid geometry": the file is likely an assembly that references separate part files. Convert the individual part files instead.
  • Part arrives at the wrong scale: STEP carries units and we honour them; if the source was authored in inches but tagged as millimetres, fix it in CAD or rescale with the STL Scale tool.
  • Multiple bodies: all solids are written into one STL. Separate them afterwards in the STL Editor.
  • Huge output: loosen the chord tolerance, or reduce the mesh with the STL Downsizer.

Going the Other Direction

Need to hand a machinist a STEP file but only have a mesh? The STL to STEP converter wraps mesh triangles as faceted B-rep faces. Be aware that it produces a faceted solid, not a parametric model — the design intent cannot be recovered from triangles.