Convert STEP to AMF
Free STEP to AMF converter that runs in your browser. See real dimensions before you download.
How to convert STEP to AMF
- 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 AMF as the output and click Convert. Several files download as one ZIP.
What carries over from STEP to AMF
| STEP | AMF | Result | |
|---|---|---|---|
| Colour / materials | Yes | Yes | Kept |
| Textures | No | No | — |
| Units stored in file | Yes | Yes | Written as mm |
| Separate parts | Yes | Yes | Kept |
| 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 AMF files
AMF was standardised as ASTM F2915 and later ISO/ASTM 52915, with the aim of fixing the shortcomings of STL for additive manufacturing. A file is XML, optionally compressed as a ZIP, and describes one or more objects made of a vertex list and volumes of triangles. Unlike STL, it declares units, such as millimetre, inch or micrometre, and can attach colours and materials to volumes or even to individual triangles, with gradients between them. The specification also allows curved triangles, constellations that arrange several objects, and custom metadata. In practice it was overtaken by 3MF, which came from industry backers and gained support in Windows and the main slicers. AMF files still appear from some multi-material printers and research tools, and from older exporters in Cura, Slic3r and Meshmixer.
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 AMF 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.
Is AMF better than STL?
On paper, yes: it has units, colour, materials and several objects. In practice STL is accepted everywhere and AMF is not, and 3MF now fills the same role with much wider support. Use AMF only when a specific tool or workflow requires it.