Is my STL file uploaded when I scale it here?

No. The file is parsed, rescaled and rebuilt in your browser with JavaScript, so it never leaves your device.

My model imports 25.4× too small or too big. Why?

STL files have no units. Most software assumes millimeters, but some CAD tools export in inches, so the same file reads 25.4× off; the "inches → mm" and "mm → inches" buttons apply that correction.

Does scaling reduce the quality of my STL?

No. Every vertex is multiplied by the same factor, so the mesh keeps the same triangles and shape. The output is binary STL, which is smaller than ASCII if your input was ASCII.

Scale STL

Resize an STL to exact dimensions or fix inch/mm unit mix-ups.

Drop an STL here or click to browse

Binary and ASCII STL supported

🔒 Scaled in your browser, never uploaded.

Scale

…or set a target size (scales uniformly)

X (mm)

Y (mm)

Z (mm)

Dimensions

	Current	After scaling
X	–	–
Y	–	–
Z	–	–

About this tool

Resize an STL without opening a slicer or CAD program. Drop a file (binary or ASCII), check its dimensions, then enter a percentage, type a target size for one axis (the others scale to match), or use the unit-fix buttons.

Those buttons fix the classic STL problem: the format stores no units, so a model designed in inches opens 25.4× too small in software that assumes millimeters. Scaling is lossless, and the result downloads as a compact binary STL with fresh normals. Everything runs in your browser, so your model is never uploaded.

Frequently asked questions

Is my STL file uploaded when I scale it here?: No. The file is parsed, rescaled and rebuilt in your browser with JavaScript, so it never leaves your device.
My model imports 25.4× too small or too big. Why?: STL files have no units. Most software assumes millimeters, but some CAD tools export in inches, so the same file reads 25.4× off; the "inches → mm" and "mm → inches" buttons apply that correction.
Does scaling reduce the quality of my STL?: No. Every vertex is multiplied by the same factor, so the mesh keeps the same triangles and shape. The output is binary STL, which is smaller than ASCII if your input was ASCII.