Is the STL in millimetres or inches?
Millimetres. STL files carry no unit, and almost every slicer assumes millimetres, so a part modelled in inches still comes in at its true size.
SLDPRT to STL
Turn a SOLIDWORKS part (.sldprt) into an STL mesh for 3D printing or a viewer, free and with no account. Pick Standard or Fine resolution. The mesh is made in your browser, so the part never leaves your computer, and it is checked against the solid before you can download it.
Your file never leaves your computer: the conversion runs in your browser.
Standard keeps every triangle within 0.05 mm of the true surface and turns no more than 5 degrees from one facet to the next. That is finer than most 3D printers lay down, and it keeps the file small. Fine tightens both to 0.01 mm and 1 degree, for large parts with gentle curves where facets would otherwise show. Fine files are larger and take longer to make.
An STL is a list of triangles. It has no idea of a hole, a fillet or a cylinder, only the facets that approximate them, which is all a slicer or a mesh viewer needs. It is not what to send a machine shop or a laser cutter: they need the exact geometry, which is what STEP carries. For that, convert SLDPRT to STEP instead.
Every body of a multi-body part goes into the one STL. The file is binary STL, in millimetres.
The STL is read back and measured against the solid it came from. Its volume may differ only by what the resolution allows, the surface area times the 0.05 mm or 0.01 mm tolerance, and its bounding box must match to within that tolerance. A mesh that came out noticeably short or swollen does not pass. The check measures volume and size only: it does not prove the mesh is closed, and a small missing face can pass.
Credits and licences for the projects the converter is built on are on the converter page.
Millimetres. STL files carry no unit, and almost every slicer assumes millimetres, so a part modelled in inches still comes in at its true size.
Standard suits almost every print: its 0.05 mm tolerance is below the layer height of a typical printer. Choose Fine for large parts with gentle curves, where small facets would otherwise show on the surface.
No converter can write SLDPRT; only SOLIDWORKS can. An STL can be made into a faceted STEP solid, but the original curved faces cannot be recovered from triangles, so keep the SLDPRT.
Lasertally is Windows software for fabrication shops. It opens STEP, IGES, DXF and NC1 files, measures the pierces, cut length and bends off the geometry, and prices the part on your own rate card.