Convert STL
to Parasolid.

Updated 2026-10-19

To convert STL to Parasolid, drop the .stl into the converter below and download an .x_t solid. Planes, cylinders, cones, spheres and tori are recognised in the triangles and usually rebuilt as true surfaces, so a round hole comes back as one cylindrical face rather than a ring of flat strips. Regions that fit none of those become smooth patches or, failing that, stay faceted, and the download says which you got. No account is needed for up to 2 solid conversions a day.

2 solid-geometry conversions a day with no account. No card, no install.

No account needed
Drop a STL file.stl · up to 200 MB
Several bodies

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

ResultSurfaces recovered

Planes, cylinders, cones and spheres are rebuilt as true surfaces where the triangles fit them, and freeform regions as smooth patches, in a closed solid that mates, measures and cuts like modelled geometry. Where they cannot be rebuilt the body is faceted instead, and every conversion says which of the two you got.

The STEP as a faceted converter writes it: 524 flat faces, one per triangle.

One face per triangle · 524 faces. Each hole is a ring of flat strips you cannot select or measure.

The STEP from MeshWeave: 10 faces, 7 planes and 3 cylinders.

MeshWeave · 10 faces: 7 planes and 3 cylinders. The hole measures Ø12.00 mm.

The same 524-triangle STL, converted both ways and coloured one shade per face. A synthetic test part, run through the converter, not drawn.

Surfaces are only as accurate as the mesh they come from, and there is no feature history.

ChangesSTL → Parasolid

What changes between STL and Parasolid

An STL is a list of triangles and nothing else: no surfaces, no edges, no unit. A Parasolid file is an exact solid; going from one to the other means deciding what the triangles were approximating, and some regions fit no simple surface at all.

That is what happens here. Groups of triangles that lie on one plane, cylinder, cone, sphere or torus are fitted, and the fit is accepted only if every vertex of the group lies within a tight tolerance of it. Accepted fits become true faces; their shared boundaries become real lines and circles. The result is a closed solid that SOLIDWORKS, Solid Edge or NX can measure, mate and machine like modelled geometry.

What it cannot do is invent accuracy or history. A coarse STL gives coarse surfaces, so start from the finest mesh you have. A variable-radius blend or a sculpted region has no simple surface to fit, so it comes back as freeform patches or facets. And there is no feature tree to recover, from this or any other tool.

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

STL file (stereolithography) (.stl)

STL is the lingua franca of 3D printing: a flat list of triangles. No unit, colour, material or history — a cylinder is a fan of flat strips. The missing unit is the classic cause of scale accidents. Every slicer and mesh tool reads it.

You are printing, meshing or sending to a bureau — where triangles are what is wanted.

Parasolid transmit file (.x_t / .x_b)

Parasolid is the modelling kernel under SOLIDWORKS, Solid Edge and NX, and a transmit file is its exact solid geometry. Between systems that share the kernel it often survives better than a neutral format. .x_t is text, .x_b is binary; both hold the same solid.

Someone in a Siemens or SOLIDWORKS shop sent you an .x_t and nothing you have opens it.

Questions11 answered
Will a hole in the STL become a real hole?
Yes, when the mesh is fine enough to show it is round: it comes back as one cylindrical face with a radius you can measure.
What if my STL has gaps or is not watertight?
Start from a closed mesh where you can. An STL with holes in it may come back as surface sheets rather than a solid.
Do I get an .x_t or an .x_b?
An .x_t, the text encoding, which is what SOLIDWORKS, Solid Edge and NX users usually exchange. The binary .x_b holds the same solid at the same precision; the encoding makes no difference to the geometry.
Should I convert to Parasolid or STEP?
Parasolid if the part is going into SOLIDWORKS, Solid Edge or NX and someone asked for it; STEP otherwise. The recovered surfaces are the same either way.
Is the STL to Parasolid converter free?
Yes. 2 solid-geometry conversions a day with no account, of 5 in total. A free account converts 4 solid files a day and adds 25 credits. No card.
Does the Parasolid result have real curves, or flat facets?
The mesh comes back as a Parasolid solid with real surfaces: a round hole becomes one cylindrical face. Planes, cylinders, cones and spheres are rebuilt as true surfaces where the triangles fit them, and freeform regions as smooth patches, in a closed solid that mates, measures and cuts like modelled geometry. Where they cannot be rebuilt the body is faceted instead, and every conversion says which of the two you got. Surfaces are only as accurate as the mesh they come from, and there is no feature history.
Will the Parasolid file open in Fusion 360, Inventor or Onshape?
Yes. Parasolid is read directly by Fusion 360, Inventor, Onshape, SOLIDWORKS, Creo, NX and FreeCAD. It usually arrives as a solid body with true surfaces, without feature history, and the conversion says when it came back faceted instead.
Can you turn the triangles back into proper CAD surfaces?
Usually. Where the triangles fit them, planes, cylinders, cones and spheres come back as true surfaces, so a hole is one cylindrical face with a radius you can measure, and freeform regions become smooth patches. Where nothing fits, the region stays faceted, and the conversion says which you got. Accuracy follows the mesh, so start from the finest STL you have.
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 STL 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 STL 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
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Going the other way? Convert Parasolid to STL.

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