Free online STP to BREP converter

Source format: stp

STP is a common file extension for STEP CAD exchange files, based on the ISO 10303 standard. It is used by engineers, manufacturers, and CAD users to share 3D product models between different design systems. Typical content includes solid geometry, assemblies, part structure, and sometimes metadata such as names, layers, or tolerances. STP files are widely used for interoperability because they preserve model geometry better than many mesh-based formats.

Target format: brep

BREP stands for boundary representation. It describes a 3D solid by its faces, edges, vertices, and the relationships between them. BREP is commonly used in CAD and modeling software for precise solid geometry, especially when downstream tools need editable, parametric, or kernel-based shapes. Its main advantages are accuracy, solid modeling compatibility, and suitability for engineering workflows.

How to perform the conversion

The best method depends on the CAD software you have, because STP to BREP is usually a geometry export or save-as operation rather than a simple file rename.

1. Open the .stp file in a CAD application that supports STEP import and BREP export, such as FreeCAD, Autodesk Fusion, SolidWorks, Rhino, or Open Cascade-based tools.
2. Check that the model imports correctly and that all parts, units, and assemblies appear as expected.
3. Use the export or save function to write the model as a .brep file. In many programs this is found under File → Export or File → Save As.
4. If your software offers format choices, select BREP, OpenCascade BREP, or a similarly named boundary-representation export option.
5. Open the resulting .brep file in the target CAD system to verify that the solid geometry was preserved.

In FreeCAD, for example, you can import the STEP file, select the imported shape or solid, then use File → Export and choose a BREP-compatible export option if available. In some workflows, the shape may need to be converted to a solid or shape first before export.

Notes on quality, compatibility, or limitations

BREP is a geometry representation, not a universal exchange format like STEP, so compatibility depends heavily on the receiving CAD kernel. A BREP file exported from one system may not open correctly in another if the software uses a different underlying geometry engine.

Because STEP files can contain assemblies and metadata, some of that information may be lost during BREP export. BREP usually preserves the shape of the model, but not necessarily product structure, constraints, materials, or annotations.

If the STEP file contains complex surfaces, imported geometry may need healing or stitching before export. Also, BREP files are often intended for single-part solids or kernel-level shapes, so large assemblies may need to be exported part by part.

For best results, ensure the STEP file is clean, watertight, and uses consistent units before converting.