stl to step (convertstltostep.com) is a free online tool that turns STL meshes into STEP files you can open in any CAD program, including SolidWorks, Fusion 360, FreeCAD, Onshape, Inventor and CATIA.
Most online converters upload your file to a server, make you wait in a queue and keep a copy for hours. We thought that was unnecessary. Modern browsers are fast enough to do the work themselves, so stl to step does everything on your device. That keeps it private, quick and free.
Our mission
3D printing and CAD still live in two separate worlds. Millions of useful parts are shared as STL files, but engineers, machinists and students need STEP to measure, modify and manufacture them. Our goal is to make that jump as simple as dropping a file into a web page, without accounts, paywalls or privacy trade-offs.
Who it’s for
- Makers who want to remix Printables or Thingiverse downloads in Fusion 360 or FreeCAD.
- Engineers bringing 3D scans and supplier meshes into their CAD system for fit checks.
- Students who need to hand in coursework in STEP format.
- Machinists who need a solid model to plan CNC toolpaths.
What makes it different
- No upload. Files are converted locally and never leave your computer or phone.
- Merge flat faces. Coplanar triangles become single CAD faces, for smaller and cleaner STEP files.
- Units & model stats. Choose mm, cm, m or inches, and check the size, volume and watertightness.
- Batch + ZIP. Convert many files at once.
- 3D viewer. Inspect your model with a turntable, wireframe, edges and snapshots.
How the conversion works
The STL is parsed (binary or ASCII), duplicate vertices are welded, and the mesh is checked for holes and consistent orientation. If you choose to, flat regions are merged into polygons. Finally, an ISO 10303-21 STEP file (AP214) is written: a closed B-rep solid for watertight meshes, or a surface model otherwise.
Our principles
- Free. No sign-ups, watermarks, daily limits or paid tiers.
- Private by design. We don’t run a conversion server, so we can’t see your files even if we wanted to.
- Honest output. We explain exactly what an STL to STEP conversion can and can’t do, with no AI promises.
Get in touch
Found a file that doesn’t convert well, or have an idea for a feature? We’d love to hear it. Email us at contact@convertstltostep.com or visit our contact page.