How To Change SolidWorks Units: The Complete Professional Guide
Changing units in SolidWorks requires modifying document properties or system defaults to ensure manufacturing-ready parametric accuracy across parts, assemblies, and drawings. Whether you need to transition from metric to imperial standards mid-project or lock down global templates, mastering the dual-unit and custom decimal configurations prevents costly downstream tolerancing errors.
Pre-Procedure Planning for Unit Management
Managing units effectively in Dassault Systèmes SolidWorks prevents unit-system mismatches that frequently cause severe parametric failures, bad mass calculations, and incorrect CNC G-code generation. Before altering any parameters, CAD technicians and design engineers must understand the scope of the change—whether it affects only the active part file, all derived drawings, or future template defaults.
- Essential gear and software versions: SolidWorks 2020 through SolidWorks 2024 (Standard, Professional, or Premium editions), access to file write permissions, and a verified administrative role if altering global system templates.
- Mandatory prerequisite knowledge: Familiarity with the SI (International System of Units) versus CGS and IPS (Inch, Pound, Second) systems, ANSI, ISO, DIN, or JIS drafting standards, and the distinction between document-level properties and system-level options.
- Estimated budget and duration benchmarks: Zero cost, 2 to 5 minutes execution time per file template.
Step-by-Step SolidWorks Unit Configuration Workflow
Step 1: Locate and Access the Document Properties Dialog Box
Open your active SolidWorks part, assembly, or drawing file. Navigate to the top menu bar, click on "Tools," and select "Options" from the drop-down menu to open the System Options / Document Properties dialog box. Alternatively, use the shortcut gear icon located at the top-right of the graphics window, or click the bottom-right status bar unit indicator and select "Edit Document Units." Ensure you are viewing the "Document Properties" tab rather than "System Options," because unit definitions are fundamentally tied to individual file architecture in SolidWorks.
Pro-Tip: You can instantly access the units menu at any time by clicking the status bar in the bottom-right corner of the SolidWorks interface where the current unit system (e.g., IPS or MMGS) is displayed.
Step 2: Select the Desired Unit System
Within the Document Properties tab, click on the "Units" subcategory located in the left-hand navigation tree. You will be presented with a choice of predefined unit systems 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 system. If your project requires custom metrics, select "Custom" to manually override individual parameters.
Step 3: Configure Precision, Decimal Places, and Tolerances
Under the unit system selection panel, configure the detailed display parameters for individual measurement types including length, angle, mass, time, and volume. For each parameter type, select your desired decimal or fractional display format and choose the exact number of decimal places (ranging from none up to 8 decimal places) to match your manufacturing tolerances.
Warning: Changing the display precision only alters how values are visualized on the screen and in drawings; it does not alter the underlying floating-point mathematical precision of the SolidWorks parametric engine.
Step 4: Save Changes as a Permanent Template for Future Projects
To prevent having to change units for every new design, save your customized unit scheme into a reusable template. Go to "File" > "Save As," select "Part Templates (.prtdot)" or "Assembly Templates (.asmdot)" from the save-as-type dropdown, and navigate to your company's standardized template folder. For enterprise environments, coordinate with your PDM (Product Data Management) administrator to update the vault standard templates so all engineering team members inherit the correct unit settings automatically.
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SolidWorks Unit Systems and Engineering Standards Comparison
| Unit System Name | Primary Length Unit | Primary Mass Unit | Primary Time Unit | Common Industry Application |
|---|---|---|---|---|
| MMGS | Millimeter (mm) | Gram (g) | Second (s) | Global mechanical engineering, automotive, ISO-compliant design |
| IPS | Inch (in) | Pound (lb) | Second (s) | US standard aerospace, heavy machinery, ANSI-compliant manufacturing |
| CGS | Centimeter (cm) | Gram (g) | Second (s) | Physics simulations, academic research, specialized scientific modeling |
| MKS | Meter (m) | Kilogram (kg) | Second (s) | Large-scale civil engineering, architectural massing, fluid dynamics |
Common SolidWorks Unit Failures and Field Fixes
- Symptom: Dimensions scale wildly or models explode after changing units.
- Root Cause: The user accidentally modified the base geometry scaling instead of the document unit display, or confused an explicit model rebuild with an import conversion.
- Actionable Fix: Revert the unit change via Ctrl+Z, ensure you are editing "Document Properties > Units" rather than scaling features, and verify that the conversion multiplier correctly matches your geometric intent.
- Symptom: Drawings retain old unit dimensions (e.g., inches) while the part file has been converted to millimeters.
- Root Cause: SolidWorks drawings maintain independent document property settings separate from their parent part files by default.
- Actionable Fix: Open the drawing file, navigate to "Tools > Options > Document Properties > Units," apply the desired unit system, and check the box to override part unit settings if necessary.
- Symptom: Mass properties calculations output astronomical or minuscule values.
- Root Cause: A unit mismatch between the selected unit system and the density assigned to the custom material (e.g., assigning g/mm³ incorrectly alongside IPS units).
- Actionable Fix: Open "Material Properties," verify that the density units match your active document unit system, or re-apply a standard material from the SolidWorks material library.
Frequently Asked Questions
How do I change units for all new parts in SolidWorks?
To apply unit changes to all future files, you must modify your default part, assembly, and drawing templates. Open a blank document, go to "Tools > Options > Document Properties > Units," select your preferred system, and save the file as a template (*.prtdot, *.asmdot, *.drwdot) in your designated template file directory specified under "System Options > File Locations."
Can I display both inches and millimeters on a SolidWorks drawing simultaneously?
Yes, you can display dual dimensions on your engineering drawings by utilizing the dual dimension functionality. Go to "Document Properties > Dimensions," locate the dual dimensions settings, and check the option to display dual units automatically or add them manually through the dimension property manager.
Why do my sketch dimensions change values when I switch unit systems?
If your sketch dimensions change numerical values when switching systems (such as 1 inch becoming 1 millimeter instead of 25.4 millimeters), it means you changed the underlying unit system while keeping the raw digit value intact rather than performing a mathematical unit conversion. Always use the standard Document Properties unit selector to ensure SolidWorks automatically calculates the correct conversion factor.
Does changing units affect existing FEA simulations or motion studies?
Yes, simulation studies and motion analysis inherit their baseline units directly from the active part or assembly document properties. If you change units mid-analysis, ensure you re-verify all applied forces, pressures, gravity vectors, and material properties to maintain physical accuracy.
Streamline your engineering workflow and eliminate manufacturing errors by standardizing your SolidWorks unit templates across your entire design team today.
