The dimension in CAD won’t show units whether we select Centimeters or Meters from “Units to scale inserted content”. To add units to dimension in CAD, we need to do settings in the “Dimension Style Manager ”

Enter D, press Enter key to open the “Dimension Style Manager”, then select ISO-25 dimension style and click “Modify” to open the “Modify Dimension Style” dialog box,

Click “Primary Units” tab, shown as below,

Click “OK” and “Close” button to close the dialog boxes.

Enter L, press Enter key, and draw a line of 50, then create a linear dimension, shown as below,

A drawing before VS After the settings