How To Change Units On SOLIDWORKS: The Complete Engineering Guide

To change units on SOLIDWORKS for an active document, click the unit system switcher located in the Status Bar at the bottom-right corner of the user interface and select your desired system, such as MMGS or IPS. For permanent changes across all future models, you must adjust the units in the Document Properties menu under System Options and save the modified file as a document template (.prtdot, .asmdot, or .drwdot). This comprehensive guide detail both rapid on-the-fly modifications and permanent template-level standardizations to keep your design engineering files highly precise and compliant with global manufacturing practices.

Pre-Configuration System Check & Unit Standards

Before modifying your unit configurations within SOLIDWORKS, you must understand how unit changes impact downstream parametric modeling, toolpath generation (CAM), finite element analysis (FEA), and technical drawing outputs. Changing units dynamically in a CAD environment alters how coordinates and parameters are written into the geometry database, though it does not physically warp or scale the 3D topology unless explicit scale features are applied.

Standardizing your CAD workspace aligns with global drafting guidelines such as ASME Y14.5 (predominately inch-based systems) or ISO metric standards. Below is the preparatory checklist required to establish unified system dimensions before generating design data.

Essential Workspace Checklist

• Software Version Compatibility: SOLIDWORKS 2018 through current releases (interfaces remain consistent across these versions).
• Active Document Files: Access to an open Part (.sldprt), Assembly (.sldasm), or Drawing (.slddrw) file to modify settings.
• Prerequisite Administrative Rights: Write access to the corporate or local CAD template file paths (often protected inside the C Drive program directories).
• Standardized Unit Schemes: Knowledge of the preferred corporate unit standard, whether Imperial (IPS: inch, pound, second) or Metric (MMGS: millimeter, gram, second; or MKS: meter, kilogram, second).
• Projected Setup Duration: Under 2 minutes for a temporary document toggle; approximately 10 to 15 minutes for complete corporate-level default template customization.

Multi-Method Workflows for Modifying SOLIDWORKS Unit Systems

Depending on whether you are adjusting a single imported file, editing an active sketch, or establishing standard corporate templates, choose the correct method below to proceed.

Step 1: Quick-Switching Units via the Graphical Status Bar

The quickest way to modify the active unit system of any open part, assembly, or drawing is to utilize the Status Bar situated on the bottom-right border of the SOLIDWORKS application interface.

1. Look to the extreme bottom-right corner of your active SOLIDWORKS window. You will see an abbreviation of the current unit system, such as MMGS or IPS.
2. Left-click directly on this unit system button. A pop-up context menu will slide upward.
3. Select one of the standard pre-configured systems from the list:
   
   
   • MKS (meter, kilogram, second)
   • CGS (centimeter, gram, second)
   • MMGS (millimeter, gram, second)
   • IPS (inch, pound, second)
   • Edit Document Units... (opens the advanced configuration menu for custom blends)
4. Once selected, the graphics area instantly updates. Any coordinate or dimension you edit henceforth will use the newly selected units.

Pro-Tip: Switching units via the Status Bar is a local change that applies only to the active document. It does not update the default settings for new documents created afterward.

Step 2: Customizing Decimal Precision and Unit Rules via Document Properties

When standard pre-built systems (like MMGS or IPS) do not offer the precise decimal places or angle notations your drafting department demands, you must modify the internal document properties.

1. Navigate to the main upper pull-down menu bar and select Tools, then click on Options (represented by a gear icon). Alternatively, click the gear icon directly at the top of the workspace.
2. Within the Options dialog box, select the Document Properties tab located at the top-left of the window.
3. On the left-hand navigation pane, select Units.
4. Under the Unit System pane, check the radio button for Custom if you want to mix metric and imperial units (for example, keeping lengths in millimeters but using pounds for mass calculations).
5. Locate the Unit table in the center of the dialog box. Under the Decimals column, click on the numerical fields to adjust precision. You can select up to eight decimal places (0.00000000) for high-precision aerospace or medical devices.
6. Configure your Dual Dimension settings if your drawings require both metric and imperial measurements displayed simultaneously.
7. Click OK at the bottom-right corner to save these configurations to the current document.

Warning: Be aware that increasing the decimal precision in Document Properties merely displays more decimal places in sketches and drawings. It does not alter the underlying solver calculations, which always operate with double-precision floating-point math.

Step 3: Making Unit Configurations Permanent via Custom Templates

If you find yourself manually changing units every time you start a new part or assembly, your default templates are configured incorrectly. To permanently set your preferred units, you must overwrite your standard templates.

1. Click the New document icon, select a standard template (Part, Assembly, or Drawing), and click OK.
2. Immediately change the unit system to your preferred layout (e.g., MMGS) using either the Status Bar or the Document Properties panel as detailed in Step 2.
3. Configure any other common standard parameters, such as drafting standards (ANSI vs. ISO) or material properties.
4. Go to the top file menu and select File > Save As...
5. In the "Save as type" dropdown list, select the corresponding template extension:
   
   
   • For Parts: Part Templates (*.prtdot)
   • For Assemblies: Assembly Templates (*.asmdot)
   • For Drawings: Drawing Templates (*.drwdot)
6. SOLIDWORKS will automatically redirect your file explorer to the default template folder (typically located at C:\ProgramData\SOLIDWORKS\SOLIDWORKS 20XX\templates). If you use custom network paths for team collaboration, navigate to that folder manually.
7. Name your template something descriptive (such as "Metric_Part_Template" or "ANSI_Inch_Part") and click Save.
8. To set this template as the absolute default, navigate to Tools > Options > System Options > Default Templates. Select your newly saved template file for Parts, Assemblies, and Drawings, and click Apply.

Step 4: Overriding Document Units on the Fly inside Sketch and Feature Dialogs

You do not have to globally change your system units just to draw a single feature in a different unit system. SOLIDWORKS possesses an integrated automatic conversion engine that accepts cross-unit inputs.

1. Open any active sketch or feature PropertyManager (such as an Extruded Boss/Base).
2. Double-click an existing dimension or open a blank dimension input box.
3. Type the numerical value followed directly by the standard unit abbreviation. For example, if your active document is set to metric (MMGS), but you want to input an exact 2-inch pin diameter:
   
   
   • Type 2in or 2" and press Enter.
4. If your document is set to imperial (IPS), and you need to input a 45-millimeter depth:
   
   
   • Type 45mm and press Enter.
5. SOLIDWORKS will calculate the mathematical conversion instantly and display the converted value in the active document's native unit system (e.g., showing 1.7717in for the 45mm input).

Default Unit Systems, Metric/Imperial Standards, and Precision Metrics

The table below outlines the core characteristics of standard SOLIDWORKS unit configurations. Choose the optimal baseline according to your sector's manufacturing capabilities.

Diagnostic Guide for Unit Conflicts & Part Scaling Failures

Even seasoned CAD professionals encounter unit bugs, especially when translating files across distinct design environments. This section covers common errors and how to fix them.

Scenario 1: Imported STEP, IGES, or Parasolid Files Load with Wrong Scales

• Root Cause: The importing CAD program exported the coordinate metadata with ambiguous scale flags, causing SOLIDWORKS to read imperial coordinates directly as metric values (for instance, reading a 10-inch part as 10 millimeters).
• Actionable Fix: Open the imported part file. Do not edit features directly. Navigate to the top menu and click Insert > Features > Scale. Select Centroid or Origin as the scaling reference. Under Scale Factor, enter the calculated translation ratio:
  
  
  • If the part is 25.4 times too small (imported inches as millimeters): Enter 25.4 as the scale factor.
  • If the part is 25.4 times too large (imported millimeters as inches): Enter 0.03937008 as the scale factor.
  • Click Checkmark to finalize the feature-level scaling.

Scenario 2: Unit Updates Do Not Reflect on Engineering Drawings

• Root Cause: The drawing sheet template relies on independent sheet format document properties, or the linked assembly's unit system is conflicting with the local sheet annotations.
• Actionable Fix: With your drawing file open, select Tools > Options > Document Properties > Units. Ensure your primary linear units match the expected manufacturing standard. If individual dimensions still fail to update, select the problematic dimension annotations directly on the drawing sheet. In their properties pane on the left, check the Override Units or Dual Dimension settings to force local system compliance.

Scenario 3: Saved Template Customizations Revert When Opening SOLIDWORKS

• Root Cause: The user-defined template was saved correctly, but SOLIDWORKS is still referencing the default program directories for new file initialization.
• Actionable Fix: Go to Tools > Options > System Options > File Locations. In the dropdown list, select Document Templates. Note the paths listed. If the default path is set to a restricted directory like C:\ProgramData, select it and click Delete. Click Add and navigate to your secure, personal, or server-mapped folder containing your customized .prtdot and .asmdot files. Click Select Folder and restart SOLIDWORKS to lock in your workspace defaults.

Scenario 4: Global Equations and Variables Fail After Unit Conversion

• Root Cause: The Equation Manager contains hardcoded constant values that lack explicit unit suffixes, which leads to computational failures when the parent system switches systems.
• Actionable Fix: Press the Equations icon in the FeatureManager design tree (or go to Tools > Equations...). Look at your global variables. If a variable is written as Length = 50, change it to Length = 50mm or Length = 1.9685in. Adding the unit suffix forces the solver to treat the value as a physical dimension rather than an abstract scalar, allowing the mathematical parameters to scale seamlessly whenever document configurations shift.

Frequently Asked Questions

How do I change units mid-sketch without changing the whole document?

You do not need to change the system settings of your document to input a foreign measurement unit. Simply click on the dimension input box within your sketch and type the foreign unit suffix (such as in, mm, cm, or m) after your numerical value. SOLIDWORKS will automatically convert that specific measurement back into the document's native unit system while maintaining the exact physical length you intended.

Why is the Status Bar unit switcher grayed out or missing?

The unit switcher on the Status Bar becomes unavailable if you do not have a document open, or if you are in the middle of a command that locks the user interface (such as a pending rebuild error or an unconfirmed property manager input). Press the Escape key to cancel active commands, rebuild the model by pressing Ctrl + B, and verify that you have a part, assembly, or drawing workspace fully active.

How do I set dual units to show metric and imperial at the same time?

To display dual dimensions on drawings or sketches, navigate to Tools > Options > Document Properties > Dimensions. Find the Dual Dimensions section and check the option to display dual dimensions. You can then specify whether the secondary unit is shown to the right of or below the primary value. This is highly useful for models processed by international manufacturing chains.

Does changing document units scale the physical geometry in SOLIDWORKS?

No, changing the unit system in the Document Properties or Status Bar does not scale the actual physical size of your design. For example, if you have a 1-inch block and you switch the document units to millimeters, the block's physical scale remains exactly the same, but the dimension callout will automatically update to display 25.4mm.

How do I change the default mass and density units for physical evaluations?

Go to Tools > Options > Document Properties > Units. Look at the Mass/Section Properties table at the bottom of the dialog box. Here, you can decouple the weight measurements from the linear units. For instance, you can construct geometry in millimeters while reporting the total mass properties in pounds or kilograms.

Optimizing Enterprise CAD Workflows

Standardizing unit configurations across your engineering department is critical to maintaining design integrity and preventing costly manufacturing scaling errors. If you want to maximize your team's output, consider deploying custom-tailored SOLIDWORKS templates and integrated PDM data workflows.