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STL to 3MF

Turn an STL into a 3MF that says its size, so a slicer does not have to guess, read back before you get it. Free, with no account or uploads.

Say the unit the STL was made in; the 3MF says millimetres in the file, and marks a shape that is not closed.

Drop an STL to turn it into a 3MF

Or choose one. For an OBJ with its MTL and pictures, or a glTF with its .bin, choose them all at once.

  • GLB
  • STL
  • OBJ
  • FBX
  • STEP
  • 3MF
  • USDZ
  • IFC
  • 3DM
  • +22 more

Stays on your device. Nothing is uploaded.

How it works and help

A little help along the way

Follow these steps. Every option is explained underneath. Everything happens in your browser; the model is never sent anywhere.

  1. Open the modelDrop it on the page or press Choose a file. An OBJ shows its colours when its .mtl file and pictures are chosen with it; a .gltf needs its .bin and pictures too. Choose them all at once.
  2. Turn it roundDrag to turn it, scroll or pinch to zoom, and drag with the right mouse button or two fingers to move it. Fit brings the whole model back into view; Front, Top, Side and Corner look at it from those sides.
  3. Say its size, if it has noneSTL, OBJ and PLY files do not say what their numbers mean. The page reads STL files in millimetres, as 3D printers and CAD programs write them; if the size looks wrong, choose the unit the file was made in.
  4. Choose how fine curves are, for CAD filesSTEP, IGES and BREP files keep exact curves, which are cut into flat triangles to be drawn. Fine suits most parts; Very fine follows curves more closely and makes a larger model, Draft a quicker, coarser one.
  5. Measure itThe size of its box is shown at once, with its surface area, and its volume when it is a closed shape. Press Measure, then two points on the model, for the distance between them; a press near a corner snaps to it.
  6. Look insideCut slices through it across its height, width or depth. Parts lists every piece by name: hide one, or press it to see which it is.
  7. Save a picturePicture saves a PNG of the model as it is shown, at the size set under More options, on a clear background if you like.

Questions people ask

Why turn an STL into a 3MF?
A 3MF says its unit in the file, so a slicer does not have to guess whether the numbers are millimetres or inches.
What if my STL has holes?
The 3MF is still written, with the shape marked as a surface rather than a solid, and the page says that a slicer may not print it.
Is the 3MF valid?
KeepSimp's 3MF files are checked in its tests by lib3mf, the 3MF Consortium's own library, in strict mode.

This page is the 3D viewer, opened for this one job; every other tool it has is one press away. Each of its settings is explained on the 3D viewer's own page.

Read the step-by-step guide

Guides

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