*Markdown alternate of . Lasertally is Windows desktop software that quotes laser-cut parts for fabrication shops from CAD files, then nests the won job on sheet or tube. Unrelated to "laser tally" in oil and gas.* STL to STEP # Convert STL to STEP. Turn an STL mesh (.stl, binary or ASCII) into a STEP file, free and with no account. The result is a faceted solid of flat faces, which CAD systems can open, measure and work against. It is built in your browser, so the file never leaves your computer, and it is checked against the mesh before you can download it. Your file never leaves your computer: the conversion runs in your browser. ## What you get, plainly An STL is a set of triangles with no record of the curved surfaces they approximated. The converter joins those triangles into a shell by the edges they share, sewing only where they do not quite meet, and, when the shell closes, a solid; it writes each triangle as one flat face of it, except that triangles lying exactly in one plane become one face. The STEP is exact to the mesh. It is not, and cannot be, the original design: a hole that was a cylinder is now a ring of flat strips, and no converter can recover the true cylinder without guessing. ## When that is useful - Getting a scanned or downloaded part into a CAD system that only opens STEP. - Measuring a mesh, or modelling a mating part against it. - Sending a part to someone whose software will not take STL. It is no substitute for the original CAD. If the part was designed in CAD, ask for its STEP file. ## Open meshes and big meshes A mesh with gaps does not close into a solid. It is converted anyway, as surfaces only, and labelled an open mesh rather than being patched shut. One loose face anywhere in the file does the same to a mesh that is otherwise closed: the whole file comes out as surfaces only. Closed bodies that touch or cross one another are not converted to STEP at all, because where they meet, which side is solid cannot be told; the page says so as soon as the file is dropped. Meshes over 30,000 triangles are refused for STEP and IGES before the converter starts: a solid made from a mesh is slow to build in a browser and large, about 1.1 KB of STEP per triangle (30,000 triangles take about half a minute to STEP and 40 seconds to IGES on a fast desktop, and make a 32 MB STEP), so reduce the mesh in your mesh or CAD software first. A mesh of more than 10,000 triangles can take up to about a minute, or more on a slower computer. ## How the STEP is checked The STEP is read back and must have every face the triangles were made into, with the same volume and surface area as the mesh to one part in a billion. Credits and licences for the projects the converter is built on are on the converter page. ## Questions ### Can STL be converted to STEP with real curved surfaces? Not exactly. An STL keeps only the triangles, so the curved surface they came from is gone. Software that offers smooth surfaces from a mesh is fitting new ones by estimate. This converter does not guess: you get the mesh, faithfully, as a solid. ### Why is the STEP file so much bigger than the STL? STEP describes every face with its own surface, edges and points, where STL lists bare triangles. A faceted solid therefore takes much more space than the mesh it came from. ### Does it read ASCII STL files? Yes. Binary and ASCII STL files are both read. The numbers in an STL are taken as millimetres, which is what almost every STL uses. ## Quoting laser-cut parts from files like these? 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. Start your free month Quoting from STEP ## Keep reading All conversions Every format pair, what is checked, and the limits. STEP to STL The other direction: an exact solid as a checked mesh. IGES to STEP Exact surfaces sewn into a STEP solid. © 2026 Lasertally LLC