Updated 2026-10-19
To convert SLDPRT to STEP, drop the .sldprt into the converter below and download the .step. Most parts come through with their own surfaces: planes stay planes and holes stay cylinders, so the STEP opens as a solid in Fusion 360, Inventor, Onshape, Creo, FreeCAD or SOLIDWORKS. A part whose own surfaces cannot be read still converts, and the result says so rather than letting a rebuilt or faceted solid pass for the exact one. Nothing is installed, and 2 solid conversions a day need no account. If the sender has SOLIDWORKS, asking them for File, Save As, STEP is just as good.
2 solid-geometry conversions a day with no account. No card, no install, no CAD licence.
On our servers. No account: deleted within 24 hours. Signed in: kept until you delete them. Never shared or used for training.
A closed STEP solid that Fusion 360, Inventor, Onshape, SOLIDWORKS, Creo and FreeCAD open directly and a machine shop can quote from. Radii measure and faces mate like modelled geometry. Where those surfaces cannot be read, or cannot be written out exactly, they are rebuilt from the display geometry, and failing that the body is faceted; every conversion says which of the three.
No feature history: you get the finished shape, not the steps that built it.
A SLDPRT is a complete SOLIDWORKS document: the finished solid plus the feature tree that built it, its sketches, configurations, material and custom properties. Only SOLIDWORKS reads all of that. STEP (ISO 10303) is the neutral exchange format, and it records the finished solid alone: faces on exact surfaces, bounded by exact edges.
So the shape comes across and the recipe does not. Where the part's own surfaces can be read, they are what you get: radii and tangency are the part's own, and a hole is one cylindrical face you can measure, mate to or machine. Where they cannot, the surfaces are rebuilt from the part's display geometry; where that does not verify either, the solid is faceted instead, the right shape in flat facets with no cylinder left to grip. Every download says which of the three it is. The feature tree, sketches and configurations stay behind, as they do when SOLIDWORKS itself saves a STEP. A multibody part keeps its bodies separate.
Nobody can turn a STEP back into a SOLIDWORKS feature tree, so be wary of any tool that says it can. If you only need to look at or measure the part, eDrawings, the free SOLIDWORKS viewer, opens a SLDPRT on Windows and macOS but does not write STEP.
A SLDPRT file is a single SOLIDWORKS part: the exact solid — true planes, cylinders and splines — plus its feature history, sketches, material and custom properties. It is proprietary, so nothing else on your machine may open it. Assemblies are SLDASM files. One SLDPRT can hold several bodies, and those should stay separate when converting.
You were sent a SLDPRT, do not have SOLIDWORKS, and need the geometry in something your CAD system, slicer or mesher opens.
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.
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.
Going the other way? Convert STEP to SLDPRT.
Need it in an older SolidWorks? Save a part for an older release.
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