Convert PLY to STL

Why convert PLY to STL?

PLY is the format of 3D scanners, photogrammetry software and research tools such as MeshLab and CloudCompare, and it often carries per-vertex colour. Slicers prefer STL, so PLY to STL is the last step before printing a scan. STL stores only triangles, which means the vertex colours are discarded, while the shape is unchanged. The more important concern is the scan itself: raw scan meshes are frequently open at the base, have holes where the scanner could not see, and contain thousands of tiny floating fragments. MeshShift reports whether the mesh is watertight and can repair it. PLY is not defined in a particular unit, so check the dimension labels to catch scans exported in metres.

How to convert PLY to STL

1. Drop your PLY file onto the converter — it opens in your browser, nothing is uploaded.
2. Check the preview and the dimensions in mm; fix units or the up axis in “Units & orientation” if the size or orientation looks wrong.
3. Choose STL as the output (binary is smaller; ASCII is human-readable) and click Convert. Several files download as one ZIP.

What carries over from PLY to STL

What changes

• Per-vertex colours are dropped; STL stores no colour.
• The triangles are preserved exactly; no remeshing or smoothing is applied.
• Point-cloud-only PLY files (no faces) cannot be converted, since STL needs triangles.
• No unit is stored in PLY, so the values are treated as millimetres unless you rescale.

Tips

• Run the print check and repair; scans nearly always have holes or a missing base.
• Large scans can be tens of millions of triangles; decimate first for a manageable STL.
• Check the dimension labels, because scanning apps often export in metres.
• If you want to keep colour for a full-colour print, use 3MF or keep the PLY.

About PLY files

PLY was developed in the mid-1990s by Greg Turk and colleagues at the Stanford Graphics Lab to store data from 3D scanners, and the Stanford Bunny and Happy Buddha models made it famous. A PLY file starts with a text header that declares elements, such as vertex and face, and the properties each element has. The body then follows in ASCII, binary little-endian or binary big-endian. Because properties are declared in the header, a file can carry any extra per-vertex data: normals, colour channels, intensity, confidence or custom scalars. This flexibility made PLY a standard output for scanners, depth cameras, photogrammetry and point-cloud tools. It can store a point cloud with no faces at all, or a polygon mesh. It does not define units or a scene structure.

About STL files

STL was created by 3D Systems in the late 1980s for its stereolithography machines, and it became the default exchange format for 3D printing. A file describes a surface as a list of triangles, each with three vertices and a facet normal. That is all it contains. There is no header field for units, no colour, no texture and no notion of separate parts. Two flavours exist: ASCII, which is readable text but large, and binary, which spends exactly 50 bytes per triangle after an 80-byte header and a 4-byte triangle count. Binary is what almost every modern tool writes. Because the format is so small and so old, every slicer, CAD package and mesh editor can read it, which is why hobbyists still download most printable models as STL from sites like Printables and Thingiverse.

3D printing notes

STL is still the safest file to hand to a slicer. Bambu Studio, PrusaSlicer, OrcaSlicer, Cura and the resin tools Chitubox and Lychee all import it, and they all treat the numbers as millimetres. The usual problems are scale (a model exported from a metre-based tool arrives 1000 times too small) and meshes that are not watertight, which makes slicers fill or skip regions. MeshShift shows the real dimensions before you convert and can scale from metres automatically. Its print check lists holes, non-manifold edges and flipped normals, and one click rebuilds a closed solid at the same size. If you need colours or several plates in one file, use 3MF instead.

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