Free online FCSTD to BREP converter

Source format: FCStd

FCStd is the native project file format used by FreeCAD, an open-source parametric 3D CAD application. An FCStd file usually contains the full design history, sketches, constraints, features, assemblies, document settings, and linked objects needed to reopen and edit a model later. It is commonly used by engineers, makers, and designers who want to preserve a fully editable CAD project rather than just a finished shape.

Because FCStd is a project container, it is best for ongoing design work, versioning, and collaboration inside FreeCAD. It is not a neutral exchange format by itself; instead, it stores the editable model data that FreeCAD uses to regenerate geometry.

Target format: BREP

BREP stands for boundary representation. It is a geometric solid/surface exchange format used by many CAD systems to store the exact shape of a model as faces, edges, and vertices. BREP files are useful when you need to transfer a solid model into another CAD program while preserving precise geometry.

The main advantage of BREP is that it is a geometry-focused format: it captures the final shape without the parametric history. This makes it widely useful for downstream CAD operations, CAM workflows, inspection, and interoperability with software that can read boundary-representation solids.

How to perform the conversion

The most reliable way to convert FCStd to BREP is with FreeCAD, since FCStd is its native format and FreeCAD can export selected solids directly as BREP.

1. Open FreeCAD.
2. Choose File → Open and load your .FCStd file.
3. In the model tree, select the final solid object you want to export. If your document contains multiple bodies or features, make sure you select the correct resulting shape, not just an early sketch or construction element.
4. Use File → Export.
5. In the file type list, choose BREP or save with a .brep extension if the exporter supports it.
6. Confirm the export and save the file.

If the model is not a single solid, you may need to first create or select a valid final shape. In FreeCAD, the exported BREP is typically the current geometric result of the selected object, not the full parametric feature history.

For batch or scripted workflows, FreeCAD’s Python console can also be used to export shapes programmatically. This is useful when you need repeatable conversions for multiple files or objects.

Notes on quality, compatibility, or limitations

BREP does not preserve parametric history. After conversion, the resulting file contains the exact geometry, but not the sketches, constraints, feature tree, or editable design logic from the FCStd project. If you need to continue editing the model in FreeCAD, keep the original .FCStd file.

Conversion quality depends on the validity of the source solid. If the FreeCAD model has broken topology, self-intersections, or incomplete features, export may fail or produce a problematic BREP file. It is best to ensure the model is fully recomputed and the final body is a clean solid before exporting.

Compatibility also varies by the receiving CAD software. While BREP is widely supported, different programs may interpret surfaces, tolerances, or naming conventions differently. If the target application has trouble reading the file, exporting a simpler, watertight solid often improves results.