Preserved
- Overall shape and physical dimensions are preserved within the selected mesh tolerance.
CAD tessellation for mechanical parts
STEP to STL Converter Online
Turn precise STEP CAD solids and assemblies into slicer-ready STL meshes. Conversion runs locally in your browser, with adjustable tessellation quality for curved surfaces.
Drop STEP or STP file here
or browse your computer
Max 100 MB · processed locally
Your model stays on this device. Parsing, conversion, verification, and download preparation run locally in this browser.
What the conversion keeps and removes
Converted
- Part placement is baked into output coordinates.
- The chosen orientation is baked into geometry.
- CAD surface orientation becomes facet normals.
Lost
- CAD topology and feature relationships are lost.
- Assembly hierarchy is lost.
- Dimensions are converted, but STL does not record a unit.
- CAD colors are lost.
- Materials and presentation properties are lost.
- Exact CAD precision, sketches, constraints, and feature history are lost.
- PMI, tolerances, and manufacturing metadata are lost.
Unsupported input
- UV reconstruction is not supported.
- Texture reconstruction is not supported.
- Cameras and lights are not converted.
- Animation is not supported.
- Print settings cannot be reconstructed.
When STEP to STL is the right workflow
Convert STEP to STL when a mechanical CAD model must move into a slicer, mesh repair tool, print quotation service, or another application that cannot read exact CAD solids. The process tessellates curved B-Rep surfaces into triangles while keeping the model’s physical dimensions in millimeters. Use the original STEP file for future engineering changes because STL does not retain sketches, constraints, features, or exact surface definitions.
- Private local STEP processing
- Adjustable CAD tessellation quality
- STEP unit normalization to millimeters
- Multi-part assembly ZIP export
- Binary STL output
- No model upload
What happens to STEP geometry
Exact surfaces become triangles
Planes, cylinders, fillets, holes, and freeform CAD surfaces are sampled into a triangle mesh. Fine quality follows small radii more closely; Draft reduces triangle count and file size.
CAD units become millimeters
The importer reads the model’s declared linear unit and normalizes geometry to millimeters, which matches the default assumption used by most consumer 3D-printing slicers.
Part boundaries remain separate
Each usable imported part is exported separately instead of silently fusing the complete assembly. Names are sanitized for safe STL filenames and duplicates receive unique suffixes.
How to convert STEP to STL
Step 1
Load and preview STEP geometry
Select a .step or .stp model up to 100 MB, then inspect detected parts, triangle count, physical dimensions, and the assumed source orientation.
Step 2
Choose tessellation and coordinates
Set Draft, Balanced, or Fine quality, confirm output unit and axis, then choose whether detected assembly parts should merge or split.
Step 3
Verify and download STL
The generated STL or ZIP is reparsed and compared with the conversion plan before the verified download is enabled.
Common STEP to STL workflows
Prototype a mechanical CAD part
Prepare brackets, enclosures, fixtures, gears, and other solid CAD parts for Cura, PrusaSlicer, Bambu Studio, or a print bureau without opening a full desktop CAD suite.
Create a supplier-ready mesh
Turn neutral STEP geometry from a customer or component supplier into an STL that can be inspected, quoted, repaired, or shared with a manufacturing workflow that accepts meshes.
Separate an assembly for printing
Export detected assembly parts as individual STL files inside one ZIP so each component can be oriented, supported, and sliced independently.
STEP and STL are different file formats
STEP is the long-form extension for ISO 10303 CAD exchange files. It stores exact curves, surfaces, solids, colors, and assembly structure. STL stores only triangles, so conversion tessellates each CAD surface into a printable mesh.
| Property | STEP | STL |
|---|---|---|
| Geometry | Exact CAD surfaces | Triangle mesh |
| Units | Defined in the file | Not explicitly stored |
| Best for | CAD exchange and editing | Slicing and 3D printing |
Fix common STEP to STL problems
- Curved surfaces look visibly faceted
- Run the conversion again with Fine mesh quality. Smaller tessellation tolerances add triangles around fillets, cylinders, threads, and other curved regions.
- The STL is too large for the slicer
- Choose Balanced or Draft quality. Excessively fine tessellation can create millions of triangles without improving the printed surface at the selected layer height.
- A part is missing from the ZIP
- Confirm that the source contains a valid solid or surface body rather than references, suppressed components, drawings, or construction geometry, then re-export the STEP from the CAD application.
STEP to STL limitations
- Exact B-Rep surfaces, curves, sketches, constraints, feature history, PMI, and engineering tolerances cannot be stored in STL.
- Wireframe-only, drawing-only, and annotation-only STEP files have no printable faces and are rejected.
- Tessellation approximates curved surfaces, so output fidelity depends on the selected mesh quality.
- STL stores unitless coordinates; confirm the displayed dimensions and selected coordinate unit before download.
STEP to STL FAQ
Is this STEP to STL converter really local?
Yes. The OpenCascade CAD engine runs in a browser worker. Your STEP model is not uploaded to a conversion server.
Does STEP to STL lose quality?
STL approximates exact CAD curves with triangles. Select Fine for smoother curved surfaces, then verify dimensions before printing.
Can it convert STEP assemblies?
Yes. Imported parts are exported as individual STL files and packaged into a ZIP when more than one part is found.
Are STEP and STP different formats?
No. STEP and STP use the same ISO 10303 file structure. Only the filename extension differs.
Same CAD format, different extension
Use the matching page if your filename uses the other common extension.