OneTaskBy Tim King · Updated
STL Dimensions
Size, Volume and Watertight Check, Free
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How the STL Dimensions Checker works
This STL dimensions checker measures a 3D print file before you slice it. Drop an .stl and the page reads its width, depth and height in millimetres and inches, its volume and surface area, what it would weigh printed solid in PLA, PETG, ABS, TPU or resin, and whether the mesh is watertight. The file is measured in your browser and never uploaded.
STL dimensions: why check before slicing
An STL file holds triangles and nothing else: no units, no scale, no material. A model from a download site might be 40 mm or 40 metres, and the only way to know is to measure it. Checking the dimensions first tells you whether it fits your build plate, whether the designer used millimetres or inches, and roughly how much material and time it will take.
How each figure is worked out
- Dimensions are the bounding box of every vertex, measured along the file's own X, Y and Z axes, so they match what a slicer shows before you rotate the part.
- Volume is calculated from the triangles using the signed tetrahedron method, which is exact for a closed mesh. It is the solid volume, before infill and shells.
- Surface area is the sum of every triangle's area.
- Solid weight is volume times a typical density: PLA 1.24, PETG 1.27, ABS 1.04, TPU 1.21 and standard resin 1.10 grams per cubic centimetre. A print at 15–20% infill usually weighs roughly a third to a half of this.
Watertight check
A printable mesh must be closed, so that every edge is shared by exactly two triangles. The checker welds matching corners and counts edges used once (holes) and edges used more than twice (non-manifold). Either kind can make the volume wrong and confuse a slicer. A small number is often repaired automatically by the slicer; hundreds mean the model needs fixing.
Units and weight to cost
If the size looks 25 times too small, the file was saved in inches; choose Inches and the figures are converted. For a price, enter the weight in the 3D print cost calculator.
FAQ
Why is the volume different from my slicer's estimate?
Slicers report the plastic actually extruded, which depends on infill, wall count and supports. This page reports the solid volume of the mesh. The two only match at 100% infill with no supports.
What does "Watertight: No" mean?
Some edges belong to only one triangle, leaving a hole, or to more than two, where surfaces meet badly. The counts are shown beside the answer. Many slicers repair small holes on import; for larger problems use a mesh repair tool before printing.
Can I check a 3MF or OBJ file?
This page reads STL only. Convert an OBJ with the OBJ to STL converter first, or open a 3MF in the 3MF viewer to see its size and parts.
See also: all 3D Model Viewers tools, Images, Audio, Video & Screen, PDF, SVG, Simulations & Screensavers, Generative Art, Chart Makers, Drawing Pads, Mockups & 3D Making, Diagram Makers, 3D Science, Tracker Music.
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