STL 3D Model Inspector (Volume, Bed Fit)
File
Inspect any STL (StereoLithography) mesh entirely in your browser — no upload. Auto-detects binary or ASCII STL, parses every triangle, and reports the count, the unique-vertex count vs raw vertex count (a measure of how aggressively the mesh shares vertices — STL stores each triangle's three vertices separately, so a watertight mesh has roughly 1/6 the unique vertices of raw), the axis-aligned bounding box, X×Y×Z size and center point, signed-tetrahedra volume (Σ (v₀ · (v₁ × v₂)) / 6 across all triangles), total surface area, and a watertight check (every undirected edge must be shared by exactly two triangles). Three orthographic SVG previews (top XY / front XZ / side YZ) let you eyeball the part, and a bed-fit table tells you which popular printers (Bambu A1 Mini / X1C, Prusa MK4, Ender 3 V3, Voron 2.4) will accept it.
How to use
- Drop a .stl file onto the dashed area or use the Choose file button.
- Switch units between mm, cm, m, and inches (STL files don't store units, so mm is the universal print convention).
- Inspect the stat grid, three orthographic projections, and the bed-fit table to see which printers will accept the part.
- Click Reset to load a different file.
Frequently asked questions
- Is my STL uploaded?
- No. The file is read with file.arrayBuffer(), parsed and rendered entirely in your browser — nothing goes to a server. You can verify by watching DevTools → Network when you load a file.
- What does 'watertight' actually mean here?
- Every interior edge in a closed mesh is shared by exactly two triangles. This tool builds a map of undirected edges and checks the count: anything but 2 means a hole, an unwelded duplicate vertex, or a non-manifold join. Slicers like PrusaSlicer / OrcaSlicer can sometimes repair small holes automatically, but a watertight mesh is required for a reliable solid volume calculation.
- How is volume computed?
- By the signed-tetrahedron method: every triangle (v₀, v₁, v₂) and the origin form a tetrahedron with signed volume (v₀ · (v₁ × v₂)) / 6. Summing across all triangles gives the enclosed volume — exact for any closed surface, regardless of where the origin is. The shown value is the absolute value so winding-order issues don't flip the sign.
- STL has no unit info — what unit is the file in?
- STL doesn't encode units. The de-facto convention for 3D printing is millimeters; for CAD exchange it's often inches. If a 100 mm cube measures 100 in this tool, it's mm. If it measures 3.94, it's probably inches. Switch units in the dropdown until the numbers match expectation.
- Why is the preview just line outlines, not shaded?
- Because SVG without WebGL can comfortably handle thousands of line segments but not depth-sorted filled polygons with shading. The orthographic outline view still tells you the silhouette and gives a quick sanity check on orientation and size — for full 3D rendering, open the STL in a slicer or a viewer like Cura / Bambu Studio.
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