SliceLoft

STL to 3MF Converter

Turn an ASCII or binary STL into a 3MF model, and check its size before downloading.

Files stay in your browser. No upload. No sign-up.

Drop an .stl file here or click to choose

ASCII or binary STL · one file at a time · up to 50 MiB / 500,000 triangles

STL has no unit field. Coordinates are treated as millimeters (mm), with no scaling. Check your model’s intended size before printing.

Geometry only: no colors, materials or print settings. The mesh is not repaired or checked for watertightness.

How to convert STL to 3MF

  1. Drop an .stl file into the box or click to choose one. ASCII and binary formats are detected automatically.
  2. Check the triangle count and dimensions in millimeters. Adjust the scale first if your original STL uses another unit.
  3. Click Download 3MF, import it as a model in your slicer, then choose the printer, filament and print settings.

A basic 3MF model for your next print

The output keeps the STL triangles, coordinates and winding, shares vertices with identical coordinates and records millimeters as the unit. One STL becomes one mesh object. ZIP compression often reduces file size, although very simple models may be larger because of the package structure.

Need to extract a mesh from an existing 3MF or inspect its objects and plates? Use the 3MF to STL converter, or browse all SliceLoft tools to choose a conversion direction.

Frequently asked questions

Is my STL file uploaded to a server?

No. Reading the file, converting the mesh and packaging the 3MF all happen in your browser. Conversion works offline after the tool page has loaded, and no account is required.

What units does STL to 3MF conversion use?

STL has no unit field. This tool keeps the original coordinate values and sets the 3MF unit to millimeters (mm). It does not detect inches or rescale the model. If the model was designed in inches, convert it to millimeters in your modeling software first, or scale it in your slicer and check its dimensions.

Will colors, materials and print settings be preserved?

No. Only triangle geometry is exported. Standard STL has no colors or materials, and nonstandard color extensions in some binary STLs are ignored. Converting to 3MF cannot restore lost colors, filament assignments or print settings.

Why convert STL to 3MF?

3MF records an explicit unit and compresses the mesh into a package for exchanging models between tools that support 3MF. The output is a basic model 3MF, not a slicer project containing printer profiles, supports or G-code. Import it as a model in your slicer, then configure the print settings.

Which STL files are supported, and is there a size limit?

Standard ASCII and binary STL are supported, one file at a time, up to 50 MiB and 500,000 triangles. Multiple solid sections in an ASCII STL become one mesh object while keeping their coordinates. Available device memory also limits the practical model size.

Does conversion repair the mesh or guarantee a printable model?

No. Incomplete STL files, invalid coordinates and zero-area triangles are rejected. Holes, self-intersections, non-manifold edges and incorrect winding are not repaired, and watertightness is not checked. Inspect the dimensions and slicing preview in your slicer after downloading.