The best way to scale an STL file 3D model is to use 3D modeling software (e.g., Blender, Fusion 360) or slicer tools (e.g., Cura, PrusaSlicer) for precise, mesh-preserving adjustments.
These tools let you enter exact percentages or dimensions, preview changes in real time, and prevent mesh distortion—critical for keeping models printable or design-accurate.
For beginners, free slicers like Cura are ideal: they have simple scaling controls and built-in mesh repair to fix minor issues after resizing.
This approach ensures your scaled model stays accurate and ready for use.