scale stl
Scale an STL online
Resize an STL by a percentage, to an exact length in millimeters, or from inches or meters to mm. Runs in your browser, then download the scaled file.
Good to know
A model that shows up tiny in the slicer was usually saved in meters or inches: ×1000 or ×25.4 fixes it. Scaling is uniform, so holes and threads grow with the part; a 3 mm screw hole at 150% is 4.5 mm. To change one size and keep the rest, make the part parametric in Voloom instead.
How it works
- 1Drop an STL, 3MF, OBJ, PLY, or GLB in the box above. It is read in your browser.
- 2Set a percentage, the length you want for the longest side, or a unit conversion such as inches to mm.
- 3Check the new size, then download the scaled file in the same format.
Why a model comes in the wrong size
STL stores numbers, not units. Slicers read them as millimeters, so a model saved in inches prints 25.4 times too small, and one in meters is a speck.
Exports from Blender, SketchUp, and game engines are often in meters, inches, or centimeters. Pick the matching conversion and check the size.
Scaling is uniform: every side, hole, and wall grows by the same factor. Thin walls get thinner when you shrink a part, so check them against your nozzle.
About STL
STL (Stereolithography). The default 3D printing format since 1987: a bare list of triangles. Every slicer reads it, but it has no units, no color, and no parts.
Units: None in the file. Slicers read the numbers as millimeters. Up axis: Z. Opens in Bambu Studio, PrusaSlicer, Cura, OrcaSlicer, and Blender.
Questions
- Is the STL scaler free?
- Yes. You get 3 runs a month without an account. Sign in with your email, free, and there is no limit.
- Is my file uploaded?
- No. The file is read and converted in your browser. It never reaches our servers.
- How do I convert an STL from inches to mm?
- Pick “×25.4 · in to mm” and download. The model keeps its shape and reads at the right size in any slicer.
- Can I scale only one side?
- This tool scales evenly, so the part keeps its proportions. To change one size and keep the holes and walls as they are, describe the part to Voloom: it builds a parametric model you can resize side by side.
Related tools
All tools- Convert STL to OBJFree STL to OBJ converter. Runs in your browser, so the file never leaves your computer. Preview the model, then download the OBJ.
- Convert STL to GLBFree STL to GLB converter. Runs in your browser, so the file never leaves your computer. Preview the model, then download the GLB.
- Convert STL to 3MFFree STL to 3MF converter. Runs in your browser, so the file never leaves your computer. Preview the model, then download the 3MF.
- Convert STL to USDZFree STL to USDZ converter. Runs in your browser, so the file never leaves your computer. Preview the model, then download the USDZ.
- Convert STL to STEPFree STL to STEP converter. Runs in your browser, so the file never leaves your computer. Preview the model, then download the STEP.
- STL viewer onlineOpen STL files in your browser. Measure distances and holes, cut a section, check it is watertight, and see the print weight. No install, nothing uploaded.
- 3MF viewer onlineOpen 3MF files in your browser. Measure distances and holes, cut a section, check it is watertight, and see the print weight. No install, nothing uploaded.
- OBJ viewer onlineOpen OBJ files in your browser. Measure distances and holes, cut a section, check it is watertight, and see the print weight. No install, nothing uploaded.