STL
STL viewer
Open any STL in 3D, measure it in mm, and see its volume, filament weight and whether it's watertight.
- Nothing uploaded
- No sign-up
- Free, no limits
Drop your STL file here
or paste it, or pick it from your device
.stl
- Drop your STL file
- Check it in 3D
- Check it's ready to print
Good to know
How to view and check an STL file
- Drop one or more STL files above. Binary and ASCII STL both work.
- Rotate, zoom and pan. The size in mm (width × depth × height) is shown straight away.
- Click Measure and pick two points to get the exact distance; points snap to corners.
- Check the volume, the filament it needs and whether it's watertight before you slice.
- Download as 3MF or OBJ if you need another format.
Your files stay on your device; nothing is uploaded.
How much filament will it use?
The viewer gives two estimates. Fully solid is the model's volume times the filament's density. Typical print assumes two walls and 15% infill, which is closer to what your slicer will report for most models. Both come with the length of 1.75 mm filament (about 2.41 cm³ per metre).
| Filament | Density | Per metre (1.75 mm) |
|---|---|---|
| PLA | 1.24 g/cm³ | ≈ 3.0 g |
| PETG | 1.27 g/cm³ | ≈ 3.1 g |
| ABS | 1.04 g/cm³ | ≈ 2.5 g |
| ASA | 1.07 g/cm³ | ≈ 2.6 g |
| TPU | 1.21 g/cm³ | ≈ 2.9 g |
Densities are typical datasheet values; brands vary slightly. Your slicer's estimate, with your settings, is the final word.
What “watertight” means
A mesh is watertight (or “manifold”) when it encloses a solid with no gaps: every edge is shared by exactly two triangles, and all faces point outwards. Slicers need that to know what's inside and what's outside. The check here reports three kinds of problem:
- Open edges: holes in the surface.
- Non-manifold edges: three or more faces meeting at one edge, common where parts overlap.
- Flipped faces: triangles facing the wrong way.
Small problems are common and most slicers repair them automatically when they load a file. For the rest, Repair STL fills holes and turns flipped faces around; overlapping parts and surfaces with no thickness (typical of game assets and some AI-generated models) need a 3D editor. When a mesh isn't closed, its volume is shown as approximate.
STL in a nutshell
STL describes a surface as a list of triangles and nothing else: no units, no colours, no parts. Every slicer reads the numbers as millimetres. It's still the most widely supported 3D printing format. If you need colours or several parts in one file, convert to 3MF.
Questions
How do I open an STL file online?
Drop it into the viewer at the top of this page. It opens in your browser on any computer or phone, with no sign-up and no upload.
Can I see the dimensions of my STL?
Yes. The width, depth and height in millimetres show as soon as the file opens, and the Measure tool gives the distance between any two points.
How do I calculate the volume and weight of an STL?
The viewer computes the volume and multiplies it by your filament's density (PLA 1.24 g/cm³, PETG 1.27, ABS 1.04 and more). You get a fully solid figure and a typical-print estimate with walls and 15% infill.
What does it mean if my STL isn't watertight?
The surface has holes, overlapping faces or flipped triangles, so it doesn't enclose a clean solid. Slicers fix small problems automatically; large holes or zero-thickness surfaces need repairing in a 3D editor first.
How do I know if my STL will print?
Check that it's watertight, that the size in mm is what you expect, and that thin parts aren't thinner than about twice your nozzle width. Then slice it and look at the preview.
Does the viewer work on Android, iPhone and Windows 11?
Yes. It runs in the browser, so there's nothing to install on any of them.