AutoCAD units are most time what you should care about before starting any project. The default units is set to inches. If you change the drawing units, you can specify whether existing objects in the drawing are scaled to the new units or retain their original size. You can also specify whether objects inserted from a drawing that uses different units are scaled to the units in the current drawing, or retain their original size.

AutoCAD Units

It is possible to draw in AutoCAD using the following units:

  • Inches
  • Feet
  • US Survey Feet
  • Miles
  • Millimeters
  • Centimeters
  • Meters
  • Kilometers
  • Microinches
  • Mils
  • Yards
  • Angstroms
  • Nanometers
  • Microns
  • Decimeters
  • Dekameters
  • Hectometers
  • Gigameters
  • Astronomical
  • Light years
  • Parsecs
  • Unitless

UNITS (Command) to set default unit

Controls the precision and display formats for coordinates, distances, and angles.

The format, precision, and other settings used to display coordinates, distances, and angles are set through this dialog box, and are saved in the current drawing. It is recommended that you save these settings to your drawing template files to reduce your setup time when you start a new drawing.

The Drawing Units dialog box is displayed.

Enter -units at the Command prompt to display options. And then click on the drop down menu under Insertion scale, select the appropriate unit and click on OK.

Options>User Preferences to control the insert block unit

Insertion Scale

Controls the default scale for inserting blocks and drawings into a drawing.

Source Content Units

If Unspecified-Unitless is selected, the object is not scaled when inserted.

Target Drawing Units

How to Convert Drawing Units from Inches to Centimeters

If you start a drawing in one system of measurement (imperial or metric) and then want to switch to the other system, use SCALE to resize the model geometry by the appropriate conversion factor to obtain correct distances and dimensions.

  1. Click Home tab – Modify panel – Scale. 
  2. At the Select Objects prompt, enter all.
  3. Enter a base point of *0,0.Scaling will be relative to the world coordinate system (WCS) origin and the location of the drawing origin will remain at the WCS origin.
  4. Enter the scale factor. To convert from inches to centimeters enter 2.54 (there are 2.54 centimeters per inch). Or, to convert from centimeters to inches enter 0.3937 (the inverse of 2.54 centimeters per inch).
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When creating precise technical drawings in AutoCAD, precise and clearly defined dimensions are crucial. However, in some cases, you may need to adjust the size to meet specific design requirements or improve the visual clarity of the graphics.

AutoCAD provides a Dimension Style Manager tool to modify dimension styles and control dimension appearance, including size.

Modify Dimension Style

Sometimes you find the dimension text is too small, the possible reason is current dimension style has been set as standard, please just select Annotative dimension style as current Style.

  • Within the PROPERTIES palette’s Misc section, click the pull-down for dimension styles, and make the appropriate selection from the list.

Note: To select multiple dimensions at one time, the Select Similar or Quick Select functions can be used

Adjust Dimension Scale

Dimension scale affects sizes, such as text height and arrowhead size, and offsets, such as the extension line origin offset.

You should set these sizes and offsets to values that represent their actual size on paper. Dimension scale does not apply the overall scale factor to tolerances or measured lengths, coordinates, or angles.

  1. Click Annotate tabDimensions panelDimension Style.
  2. In the Dimension Style Manager, Styles list, select the style you want to change.
  3. Click Modify.
  4. In Modify Dimension Style dialog box, Fit tab, under Scale for Dimension Features:
  5. Choose the Use Overall Scale Of option.
  6. Enter a value for the overall scale.
  7. Click OK.
  8. Click Close to exit the Dimension Style Manager.

Note: You can use annotative scaling to control the overall scale of dimensions displayed in layout viewports. When you create annotative dimensions, they are scaled based on the current annotation scale setting and automatically displayed at the correct size.

When you dimension model space objects in paper space using associative dimensions, dimension values for the display scale of each viewport are automatically adjusted. This adjustment is combined with the current setting for DIMLFAC and is reported by the LIST command as a dimension style override. For nonassociative dimensions, you must set DIMLFAC manually.

How to Change Text Height of a dimension?

Dimension and leader text height is controlled by the text height defined in the dimension or leader style.

Manually changing the text height of a dimension

  1. Select the dimension. 
  2. Open the Properties palette.
  3. In the Text section, change Text height to the desired value.

Changing the text height of all dimensions in a drawing

To change the text height for all of dimensions, edit the dimension style:

  1. On the command line, type DIMSTYLE (or MLEADERSTYLE), or from the Annotate tab on the ribbon tab, on the Dimensions panel, click Manage Dimension Styles, to open the Dimension Style Manager (or Multileader Style Manager).
  2. Open the Annotate tab, Select the dimension style drop down, and then select Modify Dimension Styles
  3. ​Select the dimension (or leader) style and click Modify.
  4. Select ‘Modify’ in the Dimension Styles Manager
  5. On the Text tab (or the Content tab for an mleader), set the desired text height.

The button next to the Text style menu (highlighted above) can be used to open the Text Style window in order to edit the height in the text style. You can also utilize the STYLE command if you are not inside the dimension or multileader style manager.

How to Change the Size of Arrowheads in AutoCAD

The arrowhead size is controlled by the dimension style settings.

To adjust the arrowhead size, follow these steps:

  1. Select the dimension you want to modify.
  2. Access the Dimension Style Manager by typing “DIMSTYLE” in the command line or using the appropriate icon in the Ribbon.
  3. In the Modify Dimension Style dialog box, navigate to the “Symbols and Arrows” tab.
  4. Locate the “Arrow size” option and adjust the value to increase or decrease the size of the arrowheads.
  5. Click “OK” to apply the changes.

Additional Tips for Dimension Size Adjustment

Override Dimension Style for individual dimensions

You can use the “Override” option. Simply select the dimension, right-click, and choose “Override” from the context menu. This allows you to modify the dimension size without changing the dimension style.

Use grips to adjust dimensions interactively

AutoCAD provides grips, which are small squares or triangles located on the dimension objects. By selecting these grips and dragging them, you can dynamically adjust the dimension size and position. This method is particularly useful when you need to make quick changes on the fly.

Associative dimensions

In AutoCAD, you can create associative dimensions that maintain a dynamic link with the geometry they measure. If you modify the associated geometry, the dimensions will update automatically. When changing dimension size, make sure to check if the dimensions are associative and adjust the associated geometry accordingly.

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