How To Change Units In SolidWorks: The Complete Professional Guide
Adjusting unit systems in SolidWorks is a foundational task performed via the Document Properties menu or the status bar, which instantly updates linear measurements, angular tolerances, and mass properties across the current active file. Proper configuration of these settings is critical to preventing scale errors in CNC machining, additive manufacturing, and downstream simulation analysis within the SolidWorks environment.
Pre-Procedure Prerequisites and Workflow Planning
Changing units in SolidWorks is a low-risk administrative task, but it requires an understanding of how the software handles global versus document-level settings. Before altering your design environment, ensure you are working within the correct file context—whether modifying a single Part, an Assembly, or a Drawing.
- Required Software Version: SolidWorks 2018 or newer (the interface for unit selection remains consistent across modern versions).
- Required Knowledge: Familiarity with standard ISO and ANSI dimensioning protocols and the distinction between IPS (Inch, Pound, Second) and MMGS (Millimeter, Gram, Second) systems.
- Estimated Duration: Less than 60 seconds.
- Prerequisite Checks: Verify whether you are modifying the "Document Properties" for the active file only, or updating the "System Options" for all future templates.
Step-by-Step Procedure for Modifying Document Units
Step 1: Accessing the Document Properties Interface
The primary method for unit modification is through the Options menu. With your file open, click the gear icon located in the standard toolbar at the top of the interface. If the toolbar is hidden, press the S key to bring up the shortcut menu or use the pull-down menu under Tools and select Options. In the System Options tab, navigate to the Document Properties tab. This is a critical distinction; System Options governs the interface behavior, while Document Properties governs the mathematical data of the model.
Step 2: Configuring the Unit System
Once inside the Document Properties tab, select the Units category from the left-hand navigation tree. You will be presented with a list of system presets, including IPS, MMGS, CGS, and MKS. Select the radio button corresponding to your target system. If you require a custom configuration, select Custom. In the custom view, you can independently adjust the units for length, dual dimensions, angles, length decimals, and angular decimals.
Pro-Tip: If you are working on a project that requires specific tolerances for CNC precision, always increase the Decimal Places to at least three or four positions to ensure the software does not round off critical values during manufacturing export.
Step 3: Applying Changes and Updating Status Bar
Click OK to commit the changes. Once saved, the status bar located at the bottom-right corner of the SolidWorks window will reflect the updated unit system. If you notice your dimensions are not updating immediately, select a dimension and ensure it is not hard-coded with a text override. If you need to switch units on the fly for a specific calculation, you can click the unit text directly in the status bar to toggle between common systems without navigating to the Document Properties menu.
Step 4: Propagating Units to Drawing Views
Changing units in a 3D part file does not retroactively change dimensions in existing 2D Drawings. To ensure consistency, you must open your drawing file, navigate to Document Properties, and synchronize the units there. If you frequently switch between Metric and Imperial projects, it is highly recommended to create custom Template files (.drwdot for drawings, .prtdot for parts) with your preferred unit systems pre-configured to avoid repetitive manual adjustments.
Change Dimension Settings Solidworks at Tayla Currey blog
Technical Unit Parameters and Global Comparison
The following table outlines the standard unit definitions within the SolidWorks environment, which is essential for ensuring mathematical parity between simulation, mass property calculation, and physical production.
| Unit System | Length Base | Mass Base | Time Base | Angular Base | Typical Application |
|---|---|---|---|---|---|
| MMGS | Millimeter | Gram | Second | Degree | European/ISO Manufacturing |
| IPS | Inch | Pound | Second | Degree | North American/ASME Standards |
| CGS | Centimeter | Gram | Second | Degree | Scientific/Laboratory Research |
| MKS | Meter | Kilogram | Second | Degree | Large-Scale Civil/Structural Engineering |
Common Configuration Failures and Field Remedies
Despite the simplicity of the process, users often encounter discrepancies during the transition between unit systems or when importing external CAD data.
- Root Cause: Importing IGES or STEP files that contain unit data conflicting with the current template. Actionable Fix: Always import neutral file formats into a template that matches the intended units of the source file. If the model appears oversized or undersized, use the Scale tool under the Insert menu to manually adjust the geometry if the unit conversion did not trigger automatically upon import.
- Root Cause: Dimension values displaying "inches" even after the file is set to "MMGS." Actionable Fix: Check if the dimension in the drawing or sketch has a hard-coded suffix. Double-click the dimension to open the Dimension PropertyManager and ensure the "Unit" selection is set to "Document Units" rather than a specific override.
- Root Cause: Mass properties are calculating incorrectly after a unit change. Actionable Fix: Recalculate the mass properties by selecting the "Evaluate" tab and clicking "Mass Properties." If the values remain inconsistent, verify that the material density units (e.g., kg/m3 vs. lb/in3) are accurately assigned in the Material Editor.
Frequently Asked Questions
Can I change units for only one dimension while keeping the rest of the drawing in a different system?
Yes. You can use dual dimensions to display both systems simultaneously. In the Document Properties under Units, select the "Dual dimensions and tolerances" option to show the secondary unit in parentheses next to the primary dimension.
Will changing my unit system affect the actual size of my model?
No. Changing the unit system in SolidWorks is a change in the interpretation of the mathematical values, not a geometric scale operation. Your part will maintain its exact physical dimensions, but the numeric values will be converted mathematically to match the new units.
Is it possible to set a global unit system for all new parts?
Yes. You must modify your default part, assembly, and drawing templates. Configure the units as desired, save the files as template formats (.prtdot, .asmdot, .drwdot), and set these as your default templates in the System Options > Default Templates menu.
Why is my status bar not showing the unit options?
If the status bar is missing units, your SolidWorks interface may be customized or the file might be in a read-only state. Try right-clicking the status bar to ensure "Units" is checked, or check if the file is currently being accessed as a read-only document which restricts modification of system properties.
Standardize Your CAD Engineering Workflow
Implementing consistent unit protocols across your engineering department significantly reduces the risk of expensive manufacturing errors and design misalignments. Develop and distribute standardized corporate templates today to ensure every project starts with the correct unit parameters automatically loaded.
