Convert STL mm to Inches — Fix Wrong-Size 3D Models

Rescale STEP, STL, OBJ and glTF models so they import at the right size in your slicer, CAD app or game engine.

Convert mm to inches (or cm, m, ft) on export — no more models that show up 25× too big or microscopically small.

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Free trial: 10 conversions with every feature. No credit card required. Windows 10/11.

Why Your 3D Models Import at the Wrong Size

Without 3D CAD Converter

STL opens 25× too large in Cura or PrusaSlicer because the units were wrong.
A STEP part exported in mm lands tiny in an inch-based assembly.
You eyeball a scale factor in the slicer and hope you typed it right.
Re-scaling 200 files by hand, one at a time, before every print run.

With 3D CAD Converter

Set the target unit once — every file exports at the correct real-world size.
mm → inch conversion baked into the file, so the slicer reads it right.
No guesswork: pick mm, cm, m, inch or ft and the geometry is scaled exactly.
Batch a whole folder — hundreds of models rescaled in one pass.

Get the Size Right, Every Time

mm ↔ inch & More

Convert between mm, cm, m, inch and ft. The geometry is scaled by the exact factor so your model is the right physical size on import.

Slicer-Ready Output

Export STL or OBJ already scaled to the unit your slicer expects — no more 25× surprises in Cura, PrusaSlicer or Bambu Studio.

Batch Hundreds of Files

Point at a folder, choose the target unit, and rescale every STEP, STL, OBJ or glTF in one run. Ideal for whole print queues or asset libraries.

CLI Automation

Script unit conversion with one flag and wire it into your build or print-prep pipeline. 100% offline, no cloud upload.

Rescale from the Command Line

Convert a single STL from mm to inches

cadconvert convert -i part.stl -o part_inch.stl --units in
Batch a folder of STEP files to inch-scaled STL

cadconvert batch ./parts -f stl --units in

The --units flag accepts mm, cm, in, m or ft and scales the geometry on export so it imports at the right size.

How It Works

Download & Install

Free trial: 10 conversions with every feature. Windows 10/11.

Choose Your Target Unit

Pick mm, cm, m, inch or ft as the output unit. The app scales the geometry by the exact factor as it writes the file.

Click Convert

Batch processing handles entire folders with progress tracking and ETA.

Stop Paying Annual Subscriptions

Tool	Price	Model
CAD Exchanger	~~$590/year~~	Subscription (annual renewal)
Spin 3D	~~$30/year~~	Subscription (annual renewal)
3D CAD Converter	$179	✔ Pay once, own forever

Download Free Trial Buy Now — $179

Free trial: 10 conversions with every feature. No credit card required. Windows 10/11.