STL Viewer and Volume Calculator

How to use

This tool shows an STL file in 3D and measures it for 3D printing: its size, volume and surface area, whether it's watertight, and whether it fits your printer.

1. Add an STL file: drop it on the box or choose it. 3MF, OBJ and PLY files work too, and so do STEP, GLB and glTF.
2. Drag to turn the model, scroll or pinch to zoom, and use Front, Top, Side and Angled to look from a standard direction. Full screen, in the corner of the view, gives it the whole screen. Measure gives the distance between two points you click, Cut open shows the inside, and Show problems marks a model's holes in red.
3. Read the size, volume and surface area under Details. Show sizes in switches between millimetres and inches.
4. STL files don't store a unit, so the numbers are read as millimetres, as slicers do. If the model was made in centimetres, metres or inches, choose that under File unit.
5. Watertight check says whether the model is closed, with no holes, so a slicer can print it as it is. If it isn't, it says what's wrong.
6. Under Build plate, choose your printer, or Custom size to enter its build volume. You'll see whether the model fits, whether it fits turned or lying on another side, and otherwise how far it's too big and the scale it would fit at.

The volume is the solid volume, as if the model were printed with 100% infill. A slicer prints walls and partial infill, so a real print uses less plastic.

Frequently asked questions

How is the volume worked out?

From the triangles themselves: the tool adds up the space each one encloses, which is exact for a closed model. It's the solid volume, as if printed with 100% infill, so a real print with partial infill uses less plastic. For a model with holes it's only an estimate.

What does watertight mean?

A watertight, or closed, model has no holes: every edge joins exactly two triangles, so it has a clear inside and outside. Slicers need that to know where to put plastic. They may repair a model with holes, print it wrongly or refuse it.

Why is my model the wrong size?

STL files don't store a unit. Slicers read the numbers as millimetres, so a model made in inches comes out 25.4 times too small, and one made in metres 1,000 times too big. Choose the unit it was made in under File unit.