Convert STEP
to 3DM.

Updated 2026-10-19

To convert STEP (.step / .stp) to 3DM (.3dm), drop the file below and download the result, in the browser with nothing installed. The 3DM file holds NURBS polysurfaces: the STEP solid's own faces, edges and trims.

5 conversions a day with no account. No card, no install.

No account needed
Drop a STEP file.step / .stp · up to 200 MB

On our servers. No account: deleted within 24 hours. Signed in: kept until you delete them. Never shared or used for training.

ResultExact

Each body becomes one Rhino polysurface, and a closed solid stays closed, in millimetres. Every one is checked against Rhino's own validity test before it is written; a body that would fail it is written as a mesh instead, and the result says how many.

HowThree steps
  1. Drop your .step file above — up to 200 MB without an account.
  2. 3DM is already selected as the output.
  3. Download the .3dm. Without an account, files are deleted within 24 hours; signed in, they are kept until you delete them.
FormatsWhat you are holding

STEP file (ISO 10303) (.step / .stp)

STEP (ISO 10303) is the closest thing engineering has to a universal solid format. It stores exact B-rep geometry — a hole is a cylindrical face, not a ring of facets. Fusion 360, Inventor, Onshape, SOLIDWORKS, Creo, NX, CATIA and FreeCAD all read it; .step and .stp are the same format. AP242 supersedes AP203 and AP214.

What you send when the other side has to keep modelling, quote machining, or open the shape in a different CAD system.

Rhinoceros 3D model file (.3dm)

A 3DM file is a Rhino model. Rhino is a NURBS modeller, dominant in industrial design, jewellery, marine and architecture. A 3DM can mix exact breps, surfaces, meshes and curves on layers; polysurfaces and extrusions convert exactly, and mesh objects come along: as meshes in a mesh format, rebuilt as true surfaces in a solid one.

A designer works in Rhino and engineering or manufacturing needs the shape in a format their system reads.

Questions5 answered
Is the STEP to 3DM converter free?
Yes. 5 conversions a day with no account and no card. A free account raises the limit and adds 25 credits.
Will the 3DM file keep exact curves and holes?
The 3DM file holds NURBS polysurfaces: the STEP solid's own faces, edges and trims. Each body becomes one Rhino polysurface, and a closed solid stays closed, in millimetres. Every one is checked against Rhino's own validity test before it is written; a body that would fail it is written as a mesh instead, and the result says how many.
How big a file can I convert?
To a mesh format like STL: 300 MB with a free account, 200 MB without one. To STEP, Parasolid or SLDPRT: 140 MB, because rebuilding a solid takes about twice the memory of writing a mesh. Maker and Studio convert up to 830 MB and 380 MB — a large conversion on a paid plan gets the server to itself.
Is it safe to upload my STEP file?
Files travel encrypted and are processed by machine on our own servers — no third parties, no ads or trackers, no AI training.
Is my STEP file deleted after converting?
Without an account, the upload and the result are deleted within 24 hours. With an account, both stay in your files until you delete them; deleted files leave our servers within 24 hours.
Beyond convertingSame file, four workspaces

Keep the part open: fill it with a lattice, check it with FEA, texture a surface, or slice it into cut-ready sheets. These workspaces are in early access — create an account, then apply from inside the app.

Create free account See pricing

AlsoOther ways in
MoreRelated conversions

Going the other way? Convert 3DM to STEP.

Rhinoceros® and Rhino® are registered trademarks of Robert McNeel & Associates. MeshWeave is an independent tool and is not affiliated with, endorsed by, or sponsored by Robert McNeel & Associates.