3D model to papercraft: a flat sheet to cut, fold and glue
Upload an STL or pick a cube, a dodecahedron or another regular polyhedron and get a sheet to cut, fold and glue, with numbered tabs, as a PDF at true scale.
Opens without an account 3 times a day. A free account removes the limit.
- 5 polyhedratetrahedron, cube, octahedron, dodecahedron, icosahedron
- PDF at 1:11 mm on paper is 1 mm
- Numbered tabswhat glues to what
- 800 trianglesa larger model is not unfolded
What STL to papercraft means
STL to papercraft is a free online tool from EduFacturing that unfolds a 3D mesh into a flat sheet to cut, fold and glue. The input is an STL file or one of the five regular polyhedra; the output is a PDF at true scale on A4 or A3.
Every triangle is laid on the plane at its true side lengths, so the paper is never stretched or squeezed. Where parts would overlap, the tool splits them into separate pieces instead of giving a sheet that crosses itself.
The unfolding runs in your browser, on your own computer: the file is not uploaded anywhere.
What the tool does: from STL to a paper model with tabs
Unfolds a 3D model exactly
Each triangle lands on the plane at its three true lengths. Neighbours open around the shared edge, so the paper only folds and never stretches.
Tells a fold from a seam
STL cuts even flat faces into triangles. The angle between neighbouring faces tells a real fold (dashed) from a mere diagonal on a flat face (no line).
Numbers the glue tabs
Every cut edge gets the same number on both sides and a glue tab on one side only, so it is clear which piece tucks under which.
Scales to the height you want
Say how tall the finished model should be and along which axis. The parts are packed onto as many A4 or A3 sheets as needed, with a 12 mm margin.
When you need a paper model or a cube net
Paper is a cheap prototype: a true-size model in minutes, without a plastic printer.
Cube and polyhedron nets in class
The five regular polyhedra with their exact nets: students cut, fold and count faces, edges and vertices.
A size check before printing
Before a long plastic print, fold a paper model at true scale and see whether the volume and proportions are right.
Paper figures and models
Low-poly characters, animals and buildings for hobby, decoration and scale models.
A net of a box or housing
A quick net of a box or housing to hold the shape in your hand before card or print.
How to turn a 3D model into papercraft
From STL to PDF takes five steps. Each one is in the tool's code and covered by tests.
Welding
STL stores every vertex separately. Matching vertices are merged so the tool can see which triangles share an edge.
Edges and angles
For each edge the angle between the two triangles' normals is computed. Near 0° means one plane and a seam with no line; any other angle is a fold.
Unfolding
Triangles are added one at a time at their true lengths. Before each one, the tool checks whether the new piece overlaps the placed ones (separating axis theorem). If it does, a new part starts.
Glue tabs
An edge whose two triangles end up in different places on the paper gets a shared number and a tab on one side. An edge with only one triangle is cut without a tab.
Scale and PDF
The scale is the desired height divided by the model size along the chosen axis. PDF works in points and 1 mm = 72 / 25.4 pt with no rounding, so 1 mm on the sheet is 1 mm on the print.
| Applies to | Formula | Meaning |
|---|---|---|
| Scale | s = H / h | H is the desired height in mm, h is the model size along the chosen axis |
1 mm = 72 / 25.4 pt | exact, never rounded, so the error does not grow with the sheet | |
| Fold or seam | angle between normals ≈ 0° | a triangulation seam, not drawn; otherwise a dashed fold |
| A cube in STL | 18 edges: 12 folds and 6 seams | which is why the cube comes out as 6 squares, not 12 triangles |
An unfolding that never overlaps, at exact scale
It never crosses itself
Where pieces would overlap, the unfolding splits into parts. A one-piece sheet that overlaps itself cannot be cut out.
Only real folds are drawn
Diagonals on flat faces are not drawn as lines. The cube is the familiar cross of six squares.
The scale is exact
The height you ask for in millimetres goes straight into the PDF with no rounding: the model comes out as big as you said.
There is no guarantee that an arbitrary STL unfolds into one piece without overlap. It is an open mathematical question (Shephard's conjecture), even for convex solids. The tool does not promise it: it builds the parts one by one and stops honestly.
Above 800 triangles the model is not unfolded, and the tool says plainly that it is too large instead of freezing the browser. A scanned figure or sculpture comes out as many small parts, because growth stops at the first overlap.
The printer has to be set to "Actual size" or 100 %, not "Fit to page", or the scale is lost.
Questions about STL to papercraft
How to turn STL into papercraft?
Upload the STL, choose the axis and the desired height, and download the PDF. Cut along the solid lines, fold along the dashed ones and glue each tab to the edge with the same number.
Which polyhedron nets are built in, and what does a cube net look like?
The five regular ones: tetrahedron (4 faces), cube (6), octahedron (8), dodecahedron (12) and icosahedron (20), with exact coordinates. The cube comes out as the familiar cross of six squares.
Why does my model come out in several parts?
Because in one piece some triangles would land on top of each other. The tool starts a new part instead of giving a sheet that cannot be cut out.
How large a model can be unfolded?
Up to 800 triangles. Above that the tool refuses plainly, so the browser does not freeze.
Why is my print not the right size?
Almost always the printer is set to "Fit to page". Choose "Actual size" or 100 %.
Do I need an account to unfold a model?
Without an account the tool opens 3 times a day. A free account removes the limit.
The papercraft unfolder is free. Pro opens the rest
Pro costs 15 EUR a month and opens 45 Pro tools.
In the Design group:
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Unfold your 3D model into paper
Opens without an account 3 times a day. A free account removes the limit.