How To Change The Units In SolidWorks: A Complete Professional Guide
Changing the units of measurement in SolidWorks can be done instantly using the status bar shortcut or permanently adjusted through the Document Properties panel to comply with ISO, ANSI, or custom engineering standards. Ensuring precise dimensional parameters from the start prevents costly manufacturing errors, parametric model corruption, and downstream assembly scaling conflicts.
Pre-Procedure Planning for Unit Management
Managing dimensional standards in computer-aided design requires a clear understanding of your project requirements, manufacturing tolerances, and end-user specifications before modeling begins. Establishing the correct unit system early eliminates the need for manual scaling conversions and ensures seamless integration with CNC programming software, finite element analysis tools, and 3D printing pipelines.
- Essential Gear and Software: SolidWorks 2018 or newer (Standard, Professional, or Premium editions), a fully loaded part, assembly, or drawing file, and a standard mouse with a middle scroll wheel.
- Prerequisite Knowledge & Standards: Familiarity with international measurement standards including ANSI (inch, pound, second), ISO (millimeter, gram, second), and JIS (Japanese Industrial Standards), alongside an understanding of decimal place precision requirements for machining.
- Estimated Duration and Budget: Less than 2 minutes for a single document update; zero financial cost, utilizing native built-in software settings.
Step-by-Step Guide to Modifying SolidWorks Units
Step 1: Locate the Status Bar Unit Selector
Open your SolidWorks part, assembly, or drawing file. Direct your gaze to the bottom-right corner of the main SolidWorks application window to locate the status bar. Here, you will find the active unit system currently driving your model, typically displayed as MMGS (Millimeter Gram Second), IPS (Inch Pound Second), or CGS (Centimeter Gram Second). Click directly on this text label to open a quick-selection pop-up menu showing all standard measurement systems available in the software.
Pro-Tip: Using the status bar quick-selector is ideal for rapid, temporary unit switching during client reviews, but always verify your active template settings to maintain long-term compliance with your organization's drafting standards.
Step 2: Choose Your Desired Standard System
From the expanded pop-up menu in the status bar, select your target standard measurement system. Choose MMGS for metric designs, IPS for imperial designs, or CGS / NMS depending on your specific project needs. If you require highly specialized tolerances or dual dimensions, bypass the quick menu and select Edit Document Units at the bottom of the pop-up list to open the comprehensive Document Properties dialog box.
Step 3: Configure Precision and Decimal Places
Within the Document Properties window, navigate to the Units category on the left-hand panel. Under the Unit System section, you can fine-tune individual parameter units such as length, angle, mass, and volume. Locate the Decimals drop-down menu next to your primary unit type and select the exact number of decimal places required for your manufacturing tolerances, ranging from whole numbers up to eight decimal places for high-precision aerospace or micro-machined components.
Warning: Changing decimal display precision only alters how dimensions are visualized on your screen and drawings; it does not truncate the underlying floating-point mathematical data of your parametric model features.
Step 4: Update Existing Dimensions and Drawings
Check the box labeled Update dimensions in all sketches, features, and drawings if it is available in your version dialog, ensuring that existing geometry scales appropriately to the new unit base. Click OK to commit your changes. Save your file immediately to lock in the new dimensional rules.
Step 5: Save as a Custom Document Template
To avoid repeating this setup process for every new project, save your newly configured file as a customized template. Navigate to File > Save As, select SolidWorks Part Templates (*.prtdot), Assembly Templates (*.asmdot), or Drawing Templates (*.drwdot) from the file type dropdown. Store this file in your designated company template directory so that all future designs automatically initialize with your preferred units.
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SolidWorks Unit Systems and Technical Parameters Comparison
| System Name | Length Unit | Mass Unit | Time Unit | Common Industry Application | Typical Tolerance Range |
|---|---|---|---|---|---|
| IPS | Inch (in) | Pound (lb) | Second (s) | US Aerospace, Automotive, Consumer Goods | ±0.001 in to ±0.005 in |
| MMGS | Millimeter (mm) | Gram (g) | Second (s) | Global ISO Mechanical Engineering, Medical | ±0.01 mm to ±0.05 mm |
| CGS | Centimeter (cm) | Gram (g) | Second (s) | Scientific Research, Physics Modeling | ±0.001 cm |
| MKS | Meter (m) | Kilogram (kg) | Second (s) | Large-Scale Civil Engineering, Architecture | ±0.001 m to ±0.01 m |
Troubleshooting Common SolidWorks Unit Issues
Symptom: Parts imported from STEP or IGES files appear microscopic or giant.
- Root Cause: The importing CAD software wrote the neutral file using a different default unit system than your active SolidWorks template, causing a direct 1:1 numerical translation without unit scaling.
- Actionable Fix: Go to Tools > Options > System Options > Import, select STEP or IGES from the file format list, and change the import setting from "Determined by file" to "Unit: Millimeters" or "Inches" to force proper scaling upon import.
Symptom: Drawings display metric dimensions while the underlying 3D part is modeled in inches.
- Root Cause: The drawing document properties were initialized independently of the part file, overriding the model's native unit parameters.
- Actionable Fix: Open the drawing, navigate to Tools > Options > Document Properties > Units, select your desired standard, and check the box to override or synchronize units with the inserted model views.
Symptom: Mass properties and volume calculations yield wildly incorrect figures.
- Root Cause: The unit system was changed, but the material density was not updated to reflect the new mass/volume ratio (e.g., mixing pounds per cubic inch with kilograms per cubic meter).
- Actionable Fix: Right-click Material in the FeatureManager design tree, select Edit Material, and re-apply the correct material grade to automatically recalculate density based on the active unit system.
Frequently Asked Questions
How do I change units for all new parts permanently?
Open a blank part file, set your preferred units via Tools > Options > Document Properties > Units, and save the file as a part template (*.prtdot) in your custom templates folder. Go to Tools > Options > System Options > Default Templates and browse to select your new template as the default for new parts, assemblies, and drawings.
Can I display dual dimensions (both inches and millimeters) on my drawings?
Yes. Open your drawing document properties, navigate to Units, and check the option for Dual units display. You can specify whether the secondary unit appears in brackets and set its distinct decimal precision for clear communication with international manufacturing partners.
Does changing units affect existing equations and global variables?
Changing unit systems automatically scales numerical constants defined in unit-less equations, but hard-coded dimensional values linked directly to model features will adjust their magnitude based on the conversion factor of the new unit system. Always audit your Equations dialog box after a major unit conversion to verify that design intents remain intact.
Why is the unit option grayed out in my SolidWorks file?
If you are working inside an in-context assembly or editing a part within an assembly environment, document-level properties may be locked or controlled by the top-level assembly assembly-level configurations. Open the part file in its own separate window to freely modify its core unit properties.
Mastering SolidWorks unit management streamlines your modeling workflow and ensures error-free communication between digital design environments and physical manufacturing floors.
