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How do I change the scale in AutoCAD without changing dimensions?

Published in AutoCAD Scaling 4 mins read

The key to scaling in AutoCAD without altering the displayed dimensions lies in understanding how AutoCAD handles dimensioning. Essentially, you're scaling the entire drawing, including the dimensioning objects, and then adjusting the dimension scale so that the displayed values remain correct. Here's how:

Steps to Scale Your Drawing Without Affecting Dimension Readout

  1. Select Objects to Scale: Select all the objects you want to scale, including the dimension objects themselves. Use a window selection or the 'ALL' option if you want to scale the entire drawing.

  2. Initiate the Scale Command: Type SCALE in the command line and press Enter. You can also find the Scale tool on the Modify panel of the Home tab.

  3. Specify the Base Point: Pick a base point for the scaling operation. This point will remain stationary during the scaling process.

  4. Enter the Scale Factor: Enter the desired scale factor.

    • A scale factor greater than 1 will enlarge the objects. For example, a scale factor of 2 will double the size.
    • A scale factor less than 1 will reduce the size. For example, a scale factor of 0.5 will halve the size.

  5. Adjust the Dimension Scale: This is the critical step. After scaling, your dimensions will likely display incorrect values because you’ve scaled the entire drawing, including the dimensions themselves. To correct this, you need to adjust the dimension scale (DIMSCALE) variable.

    • Using Properties Palette (Recommended): Select all your dimensions. Open the Properties Palette (Ctrl+1). Locate the "Primary Units" section, and then find the "Measurement Scale" property. Set this value to the inverse of the scale factor you used in Step 4. For example, if you scaled the drawing by a factor of 2, set the "Measurement Scale" to 0.5. If you scaled by a factor of 0.5, set the "Measurement Scale" to 2.
    • Using DIMSCALE Variable (Alternative): Type DIMSCALE in the command line and press Enter. Enter the inverse of the scale factor you used. This method can sometimes be less precise, especially with complex drawings or varying dimension styles.
    • Important Note: It's generally best practice to use annotative dimensions, especially in model space. Annotative dimensions handle scaling automatically, making this manual DIMSCALE adjustment unnecessary. Check if your dimensions are annotative, and if so, adjust the annotation scale instead to maintain the correct display.

Example

Let's say you have a rectangle with dimensions 10x20, and you want to double its size without changing the dimension readout.

  1. Select the rectangle and its dimensions.
  2. Type SCALE, specify a base point, and enter a scale factor of 2.
  3. Select all dimensions, open the Properties Palette (Ctrl+1), and change the "Measurement Scale" under "Primary Units" to 0.5. Your dimensions will now correctly display 10 and 20, despite the actual rectangle size being 20x40.

Understanding Dimension Styles

AutoCAD uses dimension styles to control the appearance and behavior of dimensions. Different dimension styles can have different DIMSCALE settings. If you have multiple dimension styles in your drawing, you may need to adjust the DIMSCALE in each relevant style by typing DIMSTYLE and modifying each as necessary to make sure all dimension styles display the correct values.

Summary

Scaling a drawing in AutoCAD without altering the displayed dimensions involves scaling the entire drawing (including the dimensions) and then adjusting the dimension scale to compensate. The most efficient method is to use the Properties Palette to modify the "Measurement Scale" of the dimensions to the inverse of the scale factor you used on the drawing. Using annotative dimensions negates the need for this process in many cases, as the annotation scale handles the dimension scaling automatically.

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