How To Change The Units In SolidWorks: A Complete Guide
Changing units in SolidWorks requires modifying both document properties for active files and system options for default templates to ensure manufacturing precision and compliance with ASME or ISO standards. This guide covers updating individual parts, assemblies, and drawings, alongside setting global defaults for future engineering designs.
Initial Setup Requirements & Document Context
Before adjusting dimensional units within SolidWorks, you must understand the distinction between active document changes and template-wide system modifications. Modifying a part file affects only that specific database, whereas altering your part, assembly, and drawing templates guarantees consistent unit scaling across all subsequent engineering projects.
- Essential Tools & Software: Dassault Systèmes SolidWorks (versions 2018 through 2024+), active part (.sldprt), assembly (.sldasm), or drawing (.slddrw) file.
- Prerequisite Knowledge: Familiarity with the SolidWorks FeatureManager Design Tree, System Options interface, and baseline understanding of SI (Metric) versus Imperial (English) drafting standards.
- Estimated Duration: Under 2 minutes for active files; 5 minutes to configure custom permanent templates.
Step-by-Step Procedure to Update SolidWorks Units
Step 1: Locate and Access the Document Properties
Open your target file in SolidWorks. Navigate to the top menu bar, click on Tools, select Options from the dropdown menu, and click on the Document Properties tab. Alternatively, you can click the gear icon on the standard toolbar, select System Options, and then switch to the Document Properties tab at the top of the dialog box.
Pro-Tip: You can access the unit settings even faster by looking at the status bar in the bottom-right corner of the SolidWorks window. Clicking directly on the unit display (e.g., MMGS or IPS) opens an immediate shortcut menu to change units on the fly.
Step 2: Select Your Desired Unit System
Inside the Document Properties menu, click on the Units category on the left-hand panel. You will see several pre-defined unit systems standard to engineering design, including MKS (Meter, Kilogram, Second), CGS (Centimeter, Gram, Second), MMGS (Millimeter, Gram, Second), and IPS (Inch, Pound, Second). Click the radio button corresponding to your desired standard.
Warning: Changing the unit system of an existing model directly scales the underlying geometry. If a cube is modeled as 10 inches and you switch the units to millimeters without scaling, the dimension text changes to 10 mm, drastically shrinking your physical part geometry.
Step 3: Customize Decimal Places and Tolerances
Under the same Units menu, look toward the lower half of the dialog box to customize specific unit types individually. You can set independent units and decimal precision for Length, Angle, Mass, Time, and Force. Adjust the Decimal places dropdown menu next to each parameter to meet your manufacturing tolerance requirements, ranging from integer values up to eight decimal places for high-precision aerospace or micro-machining components.
Step 4: Save as a Permanent Template for Future Projects
To prevent having to change units for every new file, save your customized file as a template. Go to File, select Save As, and choose *Part Templates (.prt; .sldprt)* from the save as type dropdown. Save this file directly into your designated custom templates folder, and repeat the process for assembly and drawing files if necessary.
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SolidWorks Unit Systems and Standard Tolerancing Matrix
| Unit System | Length Standard | Mass/Weight Standard | Time Standard | Common Engineering Application |
|---|---|---|---|---|
| MMGS | Millimeter (mm) | Gram (g) | Second (s) | Global mechanical design, ISO standard manufacturing, injection molding. |
| IPS | Inch (in) | Pound (lb) | Second (s) | Aerospace, defense, and heavy machinery adhering to ASME Y14.5. |
| CGS | Centimeter (cm) | Gram (g) | Second (s) | Physics simulations, academic research, specialized fluid dynamics. |
| MKS | Meter (m) | Kilogram (kg) | Second (s) | Large-scale civil engineering layouts, structural steel frameworks. |
Common SolidWorks Unit Failures and Field Fixes
- Root Cause: Dimensions appear correct in the model, but drawing views display dual dimensions or incorrect imperial fractions.
- Actionable Fix: Open the drawing document properties (Tools > Options > Document Properties > Dimensions), verify that the primary units match your manufacturing standard, and uncheck any active dual-dimension display checkboxes unless explicitly required by customer specifications.
- Root Cause: Mass properties calculations show impossibly high or low values after changing unit systems.
- Actionable Fix: Check the material assignment (Edit Material). When switching from IPS to MMGS, SolidWorks recalculates density; however, if custom material densities were manually input using weight per cubic inch, changing the unit system without updating the density scale factor leads to massive calculation errors.
- Root Cause: Changing units in a drawing view overrides the part file's native dimensions incorrectly.
- Actionable Fix: Avoid overriding dimensions manually in drawings. Always change the unit system at the part or assembly level (
.sldprtor.sldasm) so that drawing views inherit the correct associative parametric data automatically.
- Actionable Fix: Avoid overriding dimensions manually in drawings. Always change the unit system at the part or assembly level (
Frequently Asked Questions
How do I change the units of an existing SolidWorks part without resizing the geometry?
If you want to change the display units of an existing model without altering its physical dimensions, use the bottom-right status bar unit selector to switch between systems, or scale the model geometry using Insert > Features > Scale before modifying your document properties if you need to convert scale sizes intentionally.
Why won't my drawing template save my unit changes?
SolidWorks templates require you to save the file type specifically as a template (.prt, .asmt, or .drwdot). If you save a standard part file and simply rename the extension, SolidWorks will not recognize it as a valid system template for new document generation.
Can I set different units for individual dimensions on a drawing?
Yes. Click on the specific dimension in your drawing, navigate to the Dimension PropertyManager on the left side of the screen, scroll down to the Units section, uncheck Use document units, and manually select alternative precision or unit types for that single callout.
How do I set default units for all new users on a corporate network?
Administrators should configure the unit settings within a master set of part, assembly, and drawing templates, then deploy those templates company-wide using the SolidWorks File Location settings pointing to a shared server directory.
Master your CAD workflow and eliminate design errors by standardizing your SolidWorks templates today.
