Convert STL to STEP Online

Great results with:

• Mechanical parts with flat faces and cylindrical features
• 3D printed brackets, mounts, and enclosures
• Simple geometric shapes — boxes, cylinders, spheres
• Parts you need to modify dimensions on in CAD
• Models created in FreeCAD, SolidWorks, or parametric CAD tools

May struggle with:

• Organic/sculpted shapes — figurines, characters, terrain
• Very high-poly meshes (1M+ triangles)
• Complex freeform surfaces — car body panels, aircraft
• Models from photogrammetry or 3D scanning
• Models with extremely thin walls or fine details

.STL — Triangle Mesh

STL files describe 3D geometry as a collection of triangles. Every surface — no matter how smooth — is approximated by flat triangular facets. This makes STL excellent for 3D printing (slicers expect triangles) but useless for CAD editing. You can't select a "cylinder" or change a "radius" because those concepts don't exist in the format — it's just triangles.

.STEP — Mathematical Surfaces (BREP)

STEP files store geometry as mathematical surface definitions — planes, cylinders, cones, NURBS surfaces. A cylinder is represented by its center axis and radius, not by hundreds of triangles. You can select individual faces, change dimensions, add fillets, and generate engineering drawings. STEP is the ISO 10303 standard — every professional CAD system supports it.