How To Change Measurement Units In SolidWorks: A Complete Technical Guide
Changing measurement units in SolidWorks requires updating both active document properties and system-wide default templates to prevent costly manufacturing errors. This definitive guide details how to seamlessly switch between metric (MMGS) and imperial (IPS) units across parts, assemblies, and drawings while preserving dimensional accuracy and regulatory compliance.
Pre-Operation & Technical Planning Checklist
Transitioning between measurement systems in parametric CAD software demands a clear understanding of your downstream manufacturing requirements, CNC post-processor configurations, and corporate drawing standards. Failing to update system templates alongside active files can lead to silent data corruption, scaling errors during rapid prototyping, and mismatched fastener threads.
- Essential Software Requirements: SolidWorks 2020 or newer, appropriate license tier (Standard, Professional, or Premium), and administrative access to file locations if saving custom document templates.
- Mandatory Prerequisite Knowledge: Familiarity with decimal places, dual-dimensioning principles, ANSI versus ISO drafting standards, and the distinction between part-level properties and global system options.
- Time & Scope Benchmarks: Approximately 2 to 5 minutes to adjust active files; 10 to 15 minutes to reconfigure standard part, assembly, and drawing templates for permanent department-wide deployment.
Step-by-Step Procedure to Modify SolidWorks Units
Step 1: Locate and Access the Unit System Menu
Open your active SolidWorks part, assembly, or drawing file. Navigate to the lower-right corner of the graphical user interface status bar, where you will find the current unit system displayed as a clickable text string (such as MMGS, IPS, CGS, or MKS). Click directly on this status bar indicator to open a quick-selection flyout menu containing the primary measurement frameworks.
Pro-Tip: If your desired standard is not listed in the quick-selection flyout, select "Edit Document Units" at the bottom of the menu to launch the comprehensive Document Properties dialog box for advanced customization.
Step 2: Configure Custom Unit Parameters and Decimal Precision
Within the Document Properties window, ensure you are viewing the Units category under the Drafting Standard branch. Here, you can select a standard predefined system or opt for "Custom" to manually define individual parameters. Adjust the unit of length (e.g., millimeters, inches, centimeters, meters), angle, mass, and time according to your engineering specifications.
- Locate the "Unit precision" section immediately below your unit selection.
- Set the decimal places for length, mass, and volume to match your manufacturing tolerances (typically two to four decimal places for CNC machining).
- Specify the fractional display style if working with imperial architectural standards (e.g., fractions or decimals).
Warning: Changing units in an existing part does not convert the numerical value of your sketches; it merely changes the unit tag attached to that value. A 100mm extrusion will instantly become a 100-inch extrusion if you switch units without scaling or redesigning the model geometry.
Step 3: Update Mass Properties and Physical Material Density
After changing your measurement system, verify that your mass properties and density values reflect the new unit scale. Go to Evaluate from the command manager, click on Mass Properties, and check that the density unit matches your system (e.g., grams per cubic millimeter versus pounds per cubic inch). If your material database displays incorrect weight calculations, re-apply your material from the SolidWorks Material library to force an automatic recalculation based on the new unit matrix.
Step 4: Save Changes to Permanent Templates for Future Files
To prevent having to manually change units every time you open a new file, you must update your default document templates. Go to File, select Save As, and choose "Part Templates (*.prtdot)" as the file type. Navigate to your default template directory (typically hidden under ProgramData or your custom company file vault), and overwrite the existing default templates (Part.prtdot, Assembly.asmdot, and Drawing.drwdot). Alternatively, update your file locations in Tools > Options > System Options > File Locations to point SolidWorks toward a centralized, company-standard template server.
how to change units in solidworks? | GrabCAD Questions
SolidWorks Unit Systems and Engineering Standards Comparison
| Unit System | Primary Length Unit | Primary Mass Unit | Time Unit | Typical Industry Application |
|---|---|---|---|---|
| IPS | Inch (in) | Pound (lb) | Second (s) | North American aerospace, consumer products, and traditional mechanical engineering. |
| MMGS | Millimeter (mm) | Gram (g) | Second (s) | Global ISO manufacturing, automotive, medical device design, and injection molding. |
| CGS | Centimeter (cm) | Gram (g) | Second (s) | Physics simulations, academic research, and specialized fluid dynamics modeling. |
| MKS | Meter (m) | Kilogram (kg) | Second (s) | Large-scale civil engineering, heavy industrial plant layout, and architectural design. |
Common SolidWorks Unit Failures and Field Fixes
- Symptom: Model geometry appears microscopic or massively oversized immediately after switching units.
- Root Cause: The user changed the unit tag from millimeters to inches without scaling the underlying sketch and feature dimensions, causing a 25.4x geometric inflation or deflation.
- Actionable Fix: Revert the unit change immediately using Ctrl+Z. If scaling is intentional, use the Scale feature under Insert > Features > Scale to proportionally multiply or divide model geometry by the appropriate conversion factor (0.03937 for mm to inches; 25.4 for inches to mm).
- Symptom: Engineering drawings display correct dimensions, but the title block mass property custom property reads incorrect values.
- Root Cause: The Mass Properties calculation cache was generated under the old unit system and failed to refresh upon updating document properties.
- Actionable Fix: Force a complete geometry regeneration by pressing Ctrl+Q, then reopen the Mass Properties dialog box and click "Recalculate" to synchronize the custom properties with the new unit standard.
- Symptom: Newly created parts revert back to imperial units despite updating the active file settings.
- Root Cause: SolidWorks defaults to factory-installed templates stored in the default installation directory rather than your modified company templates.
- Actionable Fix: Update the file paths in Tools > Options > System Options > Default Templates to point directly to your customized part, assembly, and drawing template files.
Frequently Asked Questions
How do I display dual dimensions (both inches and millimeters) on a SolidWorks drawing?
Open your drawing document, navigate to Document Properties > Dimensions, and check the option for "Dual dimensions display." You can then specify whether the secondary unit appears in parentheses or below the primary dimension, ensuring compliance with both international and domestic manufacturing partners.
Does changing units affect existing simulation studies and FEA results?
Yes. Changing measurement systems dynamically updates the boundary conditions, forces, pressures, and material stiffness matrices within your Simulation studies. Always review your applied loads and fixture values immediately after altering a model's unit system to prevent catastrophic stress calculation errors.
Can I set different units for individual sketches without changing the entire part?
SolidWorks does not support mixed unit systems within a single part file. All features, sketches, and dimensions in a single part must adhere to the unified unit system defined in the Document Properties dialog box.
Why is the unit option greyed out in my SolidWorks file?
If your file is currently in an edit state (such as an active sketch, editing a component in an assembly, or viewing a drawing annotation), certain document property menus will lock. Close the active sketch or exit the component editing mode to regain full access to the unit configuration settings.
How can I convert imported STEP or IGES files into my preferred unit system?
When importing neutral CAD formats like STEP or IGES, open the System Options > Import menu before opening the file. Ensure that the unit setting is configured to your desired system rather than relying on the default units embedded within the incoming neutral file structure.
Master your parametric design workflow by standardizing your SolidWorks unit templates and streamlining your multi-system manufacturing pipeline today.
