How To Change Units In SolidWorks: A Complete Guide For Accurate Design
Changing units in SolidWorks requires modifying the document properties or setting up custom default templates to ensure every dimension, mass property, and manufacturing drawing aligns with strict ASME or ISO engineering standards. Whether you need to switch from Imperial (inches, pounds, seconds) to metric (millimeters, grams, seconds) for a single component or permanently update your design ecosystem, managing these parameters correctly prevents costly machining errors.
Understanding SolidWorks Unit Frameworks and Design Standards
Before altering any parameters in your SolidWorks environment, you must understand how the software categorizes units across parts, assemblies, and drawings. SolidWorks evaluates measurements dynamically, meaning a change to a dimensional property instantly updates relational geometries, extrusion values, and mass calculations. However, discrepancies often arise when users modify a part file without updating the corresponding drafting templates, resulting in dual-dimensioning conflicts or scale distortions on manufacturing blueprints.
- Essential gear, software, and system tools: SolidWorks 2020 or newer, active file access, template editing permissions.
- Mandatory prerequisite knowledge: Familiarity with parametric modeling trees, drafting standards (ASME Y14.5 or ISO 128), and basic file management.
- Estimated setup and execution duration: Under 2 minutes for active files; 5 to 10 minutes for custom template creation.
Step-by-Step Procedure to Modify Units in SolidWorks
Step 1: Access the Document Properties Menu
Open the SolidWorks part, assembly, or drawing file where you need to change the measurement system. Navigate to the top menu bar, click on Tools, select Options from the dropdown menu, and choose the Document Properties tab. Alternatively, you can use the quick-access status bar located in the bottom-right corner of the graphics window, which displays your current active unit system.
Pro-Tip: Clicking directly on the status bar unit readout at the bottom right of your screen bypasses the top menu navigation and opens the Unit Properties dialog box instantly.
Step 2: Select the Desired Unit System
Inside the Document Properties dialog box, click on the Units category on the left-side navigation panel. You will see several pre-defined standard unit systems available for selection, including IPS (inch, pound, second), MMGS (millimeter, gram, second), CGS (centimeter, gram, second), and MKS (meter, kilogram, second). Click the radio button corresponding to your required standard.
Step 3: Customize Decimal Places and Unit Precision
Below the main system selection, locate the Unit formatting section to specify the exact decimal precision for your dimensions, mass, and volumetric properties. Select individual parameters such as Length, Angle, or Mass to customize their specific decimal places or fractional display limits. Ensuring proper tolerance and decimal rounding here directly impacts the numerical readouts sent downstream to CNC programming and quality control inspection sheets.
Step 4: Apply and Save as a Custom Default Template
To prevent having to repeat this process for every new project, save your updated unit configuration as a permanent template. Go to File and select Save As, then choose *Part Templates (.prt; *.sldprt)**, *Assembly Templates (.asm; *.sldasm)**, or *Drawing Templates (.drw; .slddrw)* from the file type dropdown. Save this file into your designated company template folder and update your System Options to point to this directory for all future file creations.
Warning: Changing units in an active part file scales existing geometric dimensions unless you explicitly intend to convert the underlying numerical values rather than their physical scale. Verify whether your workflow requires a strict unit conversion or a pure unit format toggle.
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Comparative Overview of SolidWorks Unit Systems
| Unit System | Length Unit | Mass Unit | Time Unit | Common Industry Application |
|---|---|---|---|---|
| MMGS | Millimeter (mm) | Gram (g) | Second (s) | Global consumer electronics, automotive design, precision machining |
| IPS | Inch (in) | Pound (lb) | Second (s) | Aerospace, heavy machinery, North American manufacturing |
| CGS | Centimeter (cm) | Gram (g) | Second (s) | Scientific research, chemical engineering, academic modeling |
| MKS | Meter (m) | Kilogram (kg) | Second (s) | Large-scale civil engineering, structural architecture, physics simulations |
Troubleshooting Common SolidWorks Unit Discrepancies
- Root Cause: Drawings still display old unit systems or dual dimensions despite updating the part file.
- Actionable Fix: Open the drawing template, go to Document Properties, select Drafting Standard, and explicitly update the unit settings and font parameters to match the parent part file.
- Root Cause: Mass properties and center of gravity calculations appear completely incorrect after switching systems.
- Actionable Fix: Verify that the material density was not corrupted during the unit conversion process by re-applying the specific material grade from the SolidWorks Material library.
- Root Cause: New part creations continually default back to Imperial measurements despite previous changes.
- Actionable Fix: Update your default template paths via Tools > Options > System Options > File Locations to ensure SolidWorks loads your custom metric or imperial template upon startup.
Frequently Asked Questions
How do I change units for all new SolidWorks files permanently?
You must modify your default part, assembly, and drawing templates. Set your desired units via Document Properties, clear out any existing geometry, and save the empty file as a template in your designated file locations folder.
Does changing units in SolidWorks automatically scale my existing model?
SolidWorks offers options to either convert existing dimensions mathematically or keep the raw numerical values intact while changing the unit label. Always verify the conversion prompt that appears when switching between metric and imperial systems in an active part.
Can I display dual dimensions (both inches and millimeters) on a drawing?
Yes, you can enable dual dimensions by navigating to Document Properties > Dimensions and checking the option to display dual dimensions for all linear measurements automatically on engineering drawings.
Why is the status bar unit button grayed out in my drawing file?
The unit selection may be locked if the file is currently set to read-only, controlled by a PDM vault checkout state, or governed by corporate drafting standard templates that restrict manual overrides.
Master your mechanical design workflows by establishing standardized unit templates across your engineering team today.
