STL Volume and Weight Estimator

What the estimator reads out of the mesh

• Bounding-box dimensions. Every vertex is scanned once for the minimum and maximum on each axis, so X × Y × Z is the exact extent of the mesh, not an estimate.
• Triangle count and mesh health. Facets are counted as they are read, zero-area facets are reported separately, and the closure check counts edges that only one facet uses — the signature of a hole in the surface.
• Surface area. The area of every facet is summed. This is the number the shell model uses, and it is also what you need for paint, coating or plating estimates.
• Solid volume. Each triangle, its three vertices and the origin form a tetrahedron; the signed volumes are summed and the result is the volume enclosed by the mesh. It is exact arithmetic on the file's own geometry, with no sampling or approximation.
• Material volume, weight, filament length and cost. The solid volume is reduced to the material your print will actually contain, then converted with the density you choose, and the length of filament that material represents at your filament diameter.

How to use it

1. Export your model as STL from your CAD package or download it, then drag it onto the drop zone above.
2. Set the unit the STL was written in. Most exporters write millimetres; a file that looks 10× too small or too large was probably written in centimetres or inches.
3. Pick a material preset (or type your own density and spool price), then set the infill, shell thickness and filament diameter you plan to print.
4. Select Measure this STL. Change any material field afterwards and the estimate updates without re-reading the file.
5. Copy the measurement as text if you want it next to your print notes or in a filament order.

Why two material estimates instead of one number

A printed part is never just "the solid volume times the infill percentage". A 20% infill part is not 20% of its solid volume: it still has solid perimeters, solid top and bottom skins, and solid material around every hole. Two models bracket the answer:

• Infill fraction only multiplies the solid volume by the infill percentage. It ignores walls and skins completely, so it under-counts every real print. Treat it as a hard floor.
• Shell plus infill first lays a skin of the shell thickness you entered over the part's whole surface area, then fills whatever volume is left with the infill percentage. Because top and bottom skins are part of that skin, a 0% infill print still comes out with material — which is what actually happens.

The gap between the two is the value of your walls and skins. When they nearly agree, the part is thin enough that the shell already fills it, and the estimate is close to solid.

What the estimate leaves out

• Nothing about your slicer's toolpaths. Real extrusion width, layer height, infill pattern, gap fill, adaptive layers and pressure advance all move the final number. This is geometry, not a simulation.
• Support, brim, skirt, raft and purge towers. They are generated at slice time and are not in the model, so they are not in the volume. A tall overhanging part can use more support material than part material.
• Multi-material and multi-part plates. One STL is measured at a time; measuring each body and adding the figures is up to you.
• Real spool accounting. Purging, failed starts and filament left in the spool hub are not modelled here. Use the filament length and weight calculators for the spool side of that.
• Units you did not select. STL stores bare numbers. If the file was written in inches and you measure it as millimetres, every dimension is 25.4× too small and the volume 16,387× too small.

Frequently asked questions