Convert BREP to STL
Convert BREP to STL in your browser. The conversion runs on this page and the file never leaves your computer.
Result
Before you convert: what this keeps and what it destroys
Preserved
- The shape, to within the tessellation tolerance
- Overall dimensions and proportions
- Watertightness, where the input is watertight
Destroyed
- Exact curves and surfaces, replaced by triangles
- The feature tree and any parametric history
- A recorded unit: STL stores none
Why people convert BREP to STL
The usual route to a printed part when the file came out of FreeCAD, CadQuery or KiCad's 3D export.
The conversion itself is clean. Open CASCADE evaluates the exact surfaces and tessellates them, and STL wants nothing more than triangles, so nothing is lost that STL could have held.
The risk is entirely about scale, and it is worth thirty seconds of your time. Neither format records a unit. BREP is read as millimetres because that is what Open CASCADE assumes, and the STL is written on the same assumption, so the numbers pass through untouched. A part modelled in inches will slice at one twenty-fifth of its intended size and still look perfectly correct on screen. Check the overall dimensions in your slicer before you start a print.
What you get
You get a binary STL file containing triangles. The reader tessellates supported surfaces or uses saved render meshes where required by the source format. Inspect curved faces at the intended output size. The triangle count depends on the model and the reader's meshing settings.
Not carried across by this conversion: a recorded unit.
The conversion runs in your browser. Your file stays on your computer and is not uploaded.
What to check afterwards
- BREP carries no unit. The numbers in the file are just numbers, so the conversion assumes millimetres. Check the overall dimensions of the result before you commit to machining or printing it. A file exported from a package set to inches will be 25.4 times out.
- Curves become facets. BREP stores exact surfaces, so a hole is a cylinder with a radius. STL stores triangles, so that cylinder becomes a many-sided prism. Look at curved faces in the result at the size you intend to make the part.
- Coordinates are stored as 32-bit floats. For a part measured in millimetres that's far finer than any machine tolerance. For a model spanning hundreds of thousands of units it isn't.
If you need something this conversion cannot give you
If the unit has to be unambiguous, convert to 3MF instead. It records the unit in the file, so nobody downstream has to assume millimetres and nobody has to scale by 25.4 after the fact.
If you need editable CAD geometry, don't convert at all. Open the BREP file directly in FreeCAD, Fusion, Onshape or SolidWorks. Every mesh format destroys the exact surfaces, and no later conversion brings them back.
If your slicer accepts 3MF, consider it when you need a unit declaration or separate components in the output. Keep the original project for its print settings.
Going the other way
This site reads BREP but does not write it. For the reverse conversion, use an application that can export BREP.
How we know this conversion works
This pair was checked against 1 file from the test corpus on 2026-09-04. Each run parses its own output back in and compares the bounding box, the triangle count and, for closed solids, the volume against the input.
A pair that fails those checks doesn't get a page. That's why this site lists 120 conversions and not the several hundred a format-times-format grid would suggest.