Controlling line thickness is critical for professional CAD drafting. Different lineweights communicate essential manufacturing and architectural details—such as thick lines for section cuts, standard lines for visible outlines, and thin lines for thread crests or centerlines.

If your lines look wrong on-screen or print incorrectly, the fix is usually simple. Here are the four primary methods to change lineweight in AutoCAD, ranked from best practices to advanced plotting techniques.

目次

• Prerequisite: Turn On Lineweight Display
• 4 Ways to Change Lineweight
  • Method 1: Change Lineweight via Layer Properties (Recommended)
  • Method 2: Change the Global Default via the LWEIGHT Command
  • Method 3: Override via Object Properties
  • Method 4: Control Printed Thickness via Plot Style Tables
• Lineweight Priority: What Overrides What?
• Troubleshooting: Lineweights Not Displaying
• Why Lineweights Matter in CAD Drafting
• Keep Your CAD Data Clean with DARE

Prerequisite: Turn On Lineweight Display

Before you change any settings, make sure AutoCAD is actually displaying line thicknesses on your screen. By default, this feature is often turned off.

1. Navigate to the Status Bar at the bottom right of your AutoCAD window.
2. Click the Show/Hide Lineweight icon (it looks like three horizontal lines of varying thickness).
   
3. Note: If you don't see the icon, click the three horizontal lines (Customization menu) at the far right of the Status Bar and check "Lineweight" to add it to your panel.

4 Ways to Change Lineweight

Method 1: Change Lineweight via Layer Properties (Recommended)

Assigning lineweights by layer is the industry standard. It keeps your drawings organized and ensures consistency across your entire project.

1. Go to the Home tab > Layers panel > click Layer Properties.
   
2. In the Layer Properties Manager, locate the target layer and click its current Lineweight value.
   
3. Select your desired thickness (e.g., 0.30 mm) from the dialog box.
   
4. Click OK.
   
5. You have successfully changed the lineweight.

Any object on this layer with its property set to "ByLayer" will now automatically update to the new thickness.

Method 2: Change the Global Default via the LWEIGHT Command

AutoCAD applies a default thickness to all standard lines. If everything looks too thin, you can simply adjust the global default.

1. Type LWEIGHT (or LW) in the command line and press Enter.
   
2. In the Lineweight Settings dialog box, look for the Default dropdown menu.
3. Change the value from the standard 0.25 mm to your preferred thickness (e.g., 1.00 mm).
   
4. Click OK.
   
5. You have successfully changed the lineweight. Out of the box, AutoCAD's "Default" lineweight is set to 0.25 mm, as shown in the top example. By changing this "Default" value to 1.0 mm, any lines you draw will now appear at this new, heavier thickness, as shown in the bottom example.
   

Warning: You can only have one default lineweight per drawing. Changing this will alter the thickness of every layer and object currently set to use the "Default" lineweight.

Method 3: Override via Object Properties

If you need to change the thickness of a single line without affecting the rest of the layer, you can apply a direct override using the Properties palette.

1. Select the specific object(s) you want to modify.
   
2. Go to the View tab > Palettes panel > click Properties (or press Ctrl+1).
   
3. In the Properties palette, find the General section and click on Lineweight.
   
4. Select the new thickness from the dropdown list.
   

Method 4: Control Printed Thickness via Plot Style Tables

Advanced drafters use Plot Style Tables (CTB or STB) to map specific colors to specific printed lineweights. This allows you to draft with thin, brightly colored lines on a black screen, but print thick, black lines on paper or PDF.

1. Assign a specific color (e.g., Blue) to the objects you want to modify.
   
2. Open the Plot menu (Ctrl+P).
   
3. In the upper right corner, select your desired Plot Style Table (e.g., monochrome.ctb) and click the Edit icon next to it.
4. In the Form View tab, select the color you used (e.g., Color 5 - Blue).
5. Look at the properties panel on the right, find Lineweight, and choose your target thickness.
   
6. Click Save & Close, then proceed to plot your PDF or physical print.
   
7. You have successfully changed the lineweight of the blue line.
   

Lineweight Priority: What Overrides What?

If you have set a lineweight but it isn't showing up correctly, it is likely being overridden by a higher-priority setting. AutoCAD resolves conflicting settings in this exact order:

Priority	Setting Location	Behavior
1 (Highest)	Plot Style Table	Overrides all on-screen properties during printing/PDF export.
2	Object Properties	Overrides the assigned Layer settings for selected elements.
3 (Lowest)	Layer Properties	The foundational setting. Overridden by Object Properties and Plot Styles.

Example: If your Layer is set to 0.3 mm, but you change an Object Property to 0.5 mm, the line will be 0.5 mm. If your Plot Style Table dictates that all blue lines must print at 2.0 mm, that 0.5 mm line will print at 2.0 mm.

Troubleshooting: Lineweights Not Displaying

If your line thicknesses aren't showing up correctly in your workspace or during the plotting process, check out our comprehensive troubleshooting guide below:

[Reference Article]
■ Lineweights Not Showing in CAD? 5 Settings You Need to Check

Why Lineweights Matter in CAD Drafting

Different line thicknesses communicate essential information in technical drawings. In mechanical drafting, for example, specific lineweights are assigned to represent different physical features:

• Standard Lines: Visible edges and main outlines
• Thick Lines: Section lines and cutting planes
• Thin Lines: Thread roots, centerlines, and dimension lines

Industry standards (such as ISO or ASME) strictly dictate these line thicknesses to prevent manufacturing errors. Always make sure to follow your company's internal CAD standards and international drafting rules to keep your drawings accurate, readable, and highly professional.

Keep Your CAD Data Clean with DARE

Converting drawings between formats (like DWG, DXF, PDF, or STEP) often results in stripped layers, lost lineweight settings, or garbled text.

If you regularly collaborate with external teams or clients using different CAD standards, DARE makes file conversion effortless. As a cloud-based CAD translation service, DARE accurately converts your 2D and 3D files while preserving your crucial layer hierarchies and property settings—no expensive software licenses required.

Protect your design data and streamline your workflow today. Try DARE’s Free CAD Conversion Tool Now