How the STL weight calculator works
An STL is a list of triangles describing the outside of your model. MeshMath reads that list in your browser and computes three things: the enclosed volume, the surface area and the bounding box. From these it estimates how much plastic the printer will actually lay down.
1. Model volume (signed tetrahedron method)
Each triangle forms a tetrahedron with the origin. Summing their signed volumes gives the exact volume of a closed mesh:
V = | Σ (v1 · (v2 × v3)) / 6 |
2. Walls and infill
Slicers print solid perimeters and top/bottom skins, then fill the inside with sparse infill. We approximate the solid shell as surface area × wall thickness:
shell = min(V, area × wall)
plastic = shell + (V − shell) × infill%
3. Grams, metres and cost
grams = plastic (cm³) × density (g/cm³)
metres = plastic (mm³) ÷ (π × (d/2)²) ÷ 1000
cost = grams ÷ 1000 × price per kg
Common filament densities
| Material | Density (g/cm³) | 1 kg of 1.75 mm ≈ |
|---|---|---|
| PLA | 1.24 | 335 m |
| PETG | 1.27 | 327 m |
| ABS | 1.04 | 399 m |
| ASA | 1.07 | 388 m |
| TPU | 1.21 | 343 m |
| Nylon | 1.14 | 364 m |
FAQ
How much filament will my print use?
Drop your STL into the calculator above. It measures the exact model volume, then applies your infill percentage and wall thickness to estimate the plastic actually extruded, shown in grams and metres of filament.
How accurate is this STL weight calculator?
Model volume is exact for a watertight mesh. The printed weight is an estimate, usually within 10–20% of what your slicer reports, because slicers add details like top/bottom layer counts, supports, brims and purge that depend on settings.
What density should I use for PLA, PETG and ABS?
Typical values are PLA 1.24 g/cm³, PETG 1.27, ABS 1.04, ASA 1.07, TPU 1.21 and Nylon 1.14. Check your filament spool or datasheet and edit the density field if yours differs.
Is my STL file uploaded anywhere?
No. The file is read and processed entirely in your browser with JavaScript. Nothing is sent to a server.
My model looks tiny or huge — what's wrong?
STL files have no units. Most are in millimetres, but some are exported in inches. Switch the Units selector to inches if the dimensions look 25.4× too small.
How many metres are in a 1 kg spool?
About 330 m of 1.75 mm PLA, or about 130 m of 2.85 mm PLA. It varies with density and diameter.
Recommended gear
- PLA filament, 1 kg (1.75 mm) — The default for most prints; buy a known brand with tight diameter tolerance.
- PETG filament, 1 kg — Tougher and more heat-resistant than PLA for functional parts.
- Digital kitchen scale (0.1 g) — Weigh spools to see what is left; 0.1 g resolution is plenty.
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