Free online BREP to DWG converter

What the BREP format is

BREP means boundary representation: a solid or surface is described by its vertices, edges, faces, topology, and geometric definitions rather than by a mesh of triangles. Files commonly use .brep or .brp, but BREP is not one universal interchange standard; different CAD kernels can write incompatible variations.

Open CASCADE-based applications such as FreeCAD and engineering software using the Open CASCADE Technology kernel commonly create or read BREP files. You may encounter them when exporting individual solids from a CAD kernel, exchanging precise geometry between engineering programs, or saving intermediate geometry for scripting and repair operations.

What the DWG format is

DWG is Autodesk’s CAD database format, used for 2D drafting and, in some applications, 3D solids, surfaces, blocks, layers, dimensions, layouts, and annotation. AutoCAD, BricsCAD, DraftSight, and other compatible CAD programs use it for production drawings and project delivery.

DWG is preferable when recipients need editable layers and drafting objects rather than a neutral geometric exchange file. Its version matters: software may save DWG 2018, DWG 2013, or another release, and newer objects can be lost when saved to an older version.

How to actually convert BREP to DWG

For a 2D DWG drawing

1. Install FreeCAD and open the BREP file with File → Open. If direct opening is unavailable, use File → Import.
2. Check the model in the Part workbench. Repair missing faces, invalid solids, or visible gaps before generating drawing geometry.
3. Set the required view, such as front, top, or isometric, and create a planar projection with the Draft or TechDraw workbench. A projection is required because a BREP solid is three-dimensional while most DWG deliverables are 2D drawings.
4. Select the resulting curves or drawing view and use the applicable File → Export command to write drawing.dxf. FreeCAD generally exports DXF rather than DWG.
5. Open drawing.dxf in AutoCAD, BricsCAD, or DraftSight, verify units and scale, then choose Save As and select the required DWG version.

For a 3D DWG workflow

1. Import the BREP into a CAD application that supports the specific BREP variant.
2. Validate the imported object as a closed solid. A collection of surfaces may export as surfaces instead of an editable solid.
3. Export a neutral solid model such as model.step from FreeCAD if the target CAD application cannot read the original BREP.
4. Open the BREP or STEP file in a CAD system that supports 3D DWG output, then use File → Export → DWG or its equivalent. Set the DWG release, drawing units, layer mapping, and object type before exporting.
5. Reopen the resulting model.dwg in the receiving CAD application and inspect solids, surfaces, layers, and units.

For a supported file pair, you can also use the free converter on 101convert.com: choose BREP as the input and DWG as the output, upload the file, run the conversion, and download the result. The available result depends on the BREP dialect and whether the service generates 2D drawing data or preserves 3D geometry.

Quality and compatibility limitations

A direct conversion is not guaranteed because BREP describes precise model topology, whereas DWG can contain several different object types and does not define one universal method for storing imported BREP solids. Some converters create only lines and arcs; others create surfaces or proxy objects that are not fully editable in AutoCAD.

Check model units before export. BREP files may not contain reliable unit metadata, while DWG drawings interpret coordinates through insertion units and drawing settings. Confirm at least one known dimension after conversion.

Fillets, trims, NURBS surfaces, colors, material data, parametric history, constraints, and layer structure may not survive. For manufacturing or further solid modeling, retain the original BREP or export STEP alongside the DWG; use DWG primarily for drafting and coordination.