Can you change the unit system in the middle of a design in SolidWorks?
Short Answer
Yes — you can change the unit system in the middle of a design in SolidWorks using Document Properties > Units. This is the most common professional method for switching between MMGS, IPS, or other unit systems without starting over. However, changing display units does not automatically fix wrongly sized geometry if the model was created at the wrong scale.
What You Need to Know Before
Warning: In SolidWorks, changing the unit system often changes only how dimensions are displayed, not the actual model size. If the part was originally built using incorrect numeric values, sketches, features, equations, and hole callouts may still be effectively wrong after the switch.
How to Change the Unit System in the Middle of a Design
Command: Document Properties > Units
Shortcut: No default keyboard shortcut
Quick Steps:
- Open the part, assembly, or drawing, then go to Tools > Options or click the Options button on the Standard toolbar.
- In the Options dialog, open the Document Properties tab, then select Units from the left panel.
- Choose the required unit system such as MMGS, CGS, MKS, or IPS, then confirm settings like Length/Angle precision and click OK.
Variables & Settings
Key Setting: Unit System under Document Properties > Units
Expert Setting: This setting controls how dimensions, mass properties, and some annotation values are displayed for the active document. It is document-specific, not global, so changing it in one file does not update all other open or future SolidWorks files unless templates are also updated.
Why it Fails
- Cause 1 (Geometry): The model was created with incorrect entered values, so changing units only relabels dimensions instead of resizing the geometry correctly.
- Cause 2 (layers/Locks): In drawings, linked dimensions, title block notes, or custom properties may still show old unit text because annotation formatting or note text was manually overridden.
- Cause 3 (Command/Logic): Assemblies can become inconsistent when inserted components use different document unit settings, especially when users assume the unit change converts all referenced files the same way.
Quick Fix & Best Practice
- Quick Fix: Use Tools > Options > Document Properties > Units first, then verify a known dimension with Measure to confirm whether only display units changed or the model size is actually correct.
- Manager’s Verdict: Change units mid-design only when the geometry was modeled correctly and you just need a different display standard. If the part was built at the wrong scale, remodel or use a controlled scaling workflow instead of relying on a unit switch.
FAQ
Does changing units in SolidWorks resize the model?
No, it typically changes the displayed unit format, not the physical geometry size.
Can I use different units in different SolidWorks files?
Yes, unit settings are document-specific unless controlled through templates.
Should I change units in the part or in the drawing?
Prefer changing them in the source part or assembly first, then confirm the drawing displays the intended unit standard.
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