Convert STEP to OFF
Free STEP to OFF converter that runs in your browser. See real dimensions before you download.
How to convert STEP to OFF
- Drop your STEP file onto the converter — it opens in your browser, nothing is uploaded.
- Check the preview and the dimensions in mm; fix units or the up axis in “Units & orientation” if the size or orientation looks wrong.
- Choose OFF as the output and click Convert. Several files download as one ZIP.
What carries over from STEP to OFF
| STEP | OFF | Result | |
|---|---|---|---|
| Colour / materials | Yes | No | Dropped |
| Textures | No | No | — |
| Units stored in file | Yes | No | Numbers in mm |
| Separate parts | Yes | No | Merged into one mesh |
| Usual up axis | Z | Z | Unchanged |
About STEP files
STEP, formally ISO 10303 and known as the Standard for the Exchange of Product model data, has been developed since the 1980s and is the main neutral format for moving CAD models between companies and systems. The usual application protocols are AP203 and AP214 for geometry and assemblies, and AP242 for modern product and manufacturing information. A .step or .stp file is plain text written in the EXPRESS-based Part 21 syntax. Unlike STL, it does not store triangles: it stores boundary representation (B-rep) geometry, meaning exact planes, cylinders, splines and NURBS surfaces joined by edges and faces into solids. That keeps holes perfectly round and dimensions precise, and allows the receiving CAD to keep editing faces. Files can contain assemblies, product structure, colours and units.
About OFF files
OFF, the Object File Format, was defined for Geomview, an interactive geometry viewer developed at the Geometry Center at the University of Minnesota in the 1990s. A file is plain text. The first line holds the keyword OFF, the second gives the counts of vertices, faces and edges, then each vertex appears as three coordinates and each face as a vertex count followed by index numbers. Variants add colour (COFF), normals (NOFF) or texture coordinates (STOFF) through prefixes, and colour is optional at the end of each line. The simplicity made it a favourite in computational geometry, and benchmark sets such as ModelNet used it for machine-learning research on shape classification. CGAL and libigl read and write it directly. It has no units, materials or scene structure, so it is rarely a printing format, but converting it is common.
3D printing notes
Most slicers cannot read STEP, though some, like PrusaSlicer, will import it and mesh it internally, so the usual step is exporting STL or 3MF from your CAD program. Tessellation quality decides how smooth the printed curves look: too coarse and cylinders become visible facets, too fine and files grow huge. MeshShift reads STEP and STP using OpenCascade in the browser and lets you pick draft, normal or fine tessellation. When it writes STEP, the result is a faceted B-rep: a solid made of flat triangular faces, not a parametric CAD model, so it will not give you editable holes or fillets. Use it to exchange a mesh as a solid, not to recover design intent.
Frequently asked questions
Is this STEP to OFF converter free and private?
Yes. The conversion runs in your browser with JavaScript and WebAssembly, so your STEP file is never uploaded to a server. There is no sign-up, no watermark and no daily limit; very large files are limited only by your device's memory.
What is the difference between STEP and STP?
Nothing in the content. Both extensions hold the same ISO 10303 Part 21 text; .stp exists because older systems limited extensions to three letters. Any program that reads one reads the other, and renaming the file is enough.
What is an OFF file used for?
OFF is a simple mesh format used mainly in geometry processing and machine-learning research. Datasets like ModelNet ship as OFF because the format is easy to parse. It is a plain text list of vertices and faces.