STL Volume Calculator
Open a binary or ASCII STL file in your browser and get its volume, bounding box, a closed-mesh check and the solid weight in PLA, PETG, ASA or your own material.
The file is read in your browser and never uploaded.
Choose an STL file to see its volume, size and weight.
How to find the volume of an STL file
- Choose the file. Pick a binary or ASCII .stl file. It is read in your browser and never leaves your device.
- Set the units. STL files have no units. Most 3D printing models are in millimetres; switch to centimetres or inches if the size looks wrong.
- Pick a material. Choose PLA, PETG or ASA, or enter the density from your own filament or resin data sheet.
- Read the result. You get the volume, the bounding box, whether the mesh is closed and the solid weight.
10 situations where an STL volume helps
Quoting a resin print
Resin is sold by volume, so the model's ml is the starting point for a price before supports.
Checking a model fits the build plate
The bounding box shows X, Y and Z before the file is opened in a slicer.
Estimating a solid print's weight
A solid PLA part's weight is volume × 1.24 g/cm³; a printed part with infill weighs less.
Finding a broken mesh
The closed-mesh check counts open edges, which also cause slicing errors.
Casting from a 3D-printed master
The model's volume is the amount of resin or metal a mold of it will hold.
Spotting a unit mix-up
A 2 mm part that should be 50 mm was exported in inches; the size makes that obvious.
Comparing design revisions
Load two versions and compare how much material each one uses.
Checking a file without installing software
No CAD program or slicer is needed to read the volume.
Sending a file to a print service
Knowing the volume first gives a sense of the quote before uploading anywhere.
Working with confidential parts
Because nothing is uploaded, a client's part stays on your machine.
How the volume is worked out
An STL file lists triangles. Each triangle and the origin form a tetrahedron whose signed volume is v1 · (v2 × v3) ÷ 6. Adding these over a closed surface cancels everything outside the solid and leaves its volume. This is the method in Cha Zhang and Tsuhan Chen's 2001 paper 'Efficient feature extraction for 2D/3D objects in mesh representation' (ICIP 2001).
Both STL forms are read. Binary STL is an 80-byte header, a 32-bit triangle count and 50 bytes per triangle, as described by the Library of Congress format description; a file whose size matches that layout is read as binary even if its header begins with 'solid'. Otherwise the file is read as ASCII 'vertex x y z' lines.
The closed-mesh check joins identical vertices and counts edges that are not shared by exactly two triangles. Weight is volume × density; the PLA (1.24), PETG (1.27) and ASA (1.07 g/cm³) figures are from Prusament's technical data sheets (ISO 1183).
Limits: the result is the solid volume. Printed parts with infill and walls, and resin prints with supports, use a different amount — the slicer reports that. If the mesh is open the volume is not meaningful. STL stores no units, so the unit you choose is an assumption.
Sources
- Zhang & Chen, ICIP 2001 (Cornell) — Signed volume of tetrahedra summed over a mesh
- Library of Congress: STL binary format — 80-byte header, uint32 count, 50 bytes per facet, little-endian
- Prusament PLA technical data sheet — Density 1.24 g/cm³
- Prusament PETG technical data sheet — Density 1.27 g/cm³
- Prusament ASA technical data sheet — Density 1.07 g/cm³
Frequently asked questions
How do I calculate the volume of an STL file?
Sum the signed volumes of the tetrahedra formed by each triangle and the origin. This page does that in your browser when you choose the file.
Is my file uploaded?
No. The file is read with your browser's file API and processed on your device.
What units are STL files in?
None are stored. Most 3D printing software treats the numbers as millimetres, so that is the default.
Why does it say my mesh is not closed?
Some edges belong to only one triangle (a hole) or to more than two. The volume of an open surface is not defined, so repair the mesh first.
Why is my print lighter than the weight shown?
The weight assumes a solid part. Prints with infill have hollow space inside; your slicer's estimate accounts for that.
How much resin will my STL print use?
At least the solid volume shown, in ml, plus supports and the base, which depend on your print settings.
Does it handle large files?
Yes, up to 10 million triangles, limited by your device's memory.
What about OBJ or 3MF files?
This page reads STL only. Most modelling software can export STL.
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