To Delete Dimensions
When working with added dimensions (dimensions created with the > 
Dimension command.) you can either erase or delete the dimensions. Deleting the dimensions permanently removes them from the drawing.
Dimension command.) you can either erase or delete the dimensions. Deleting the dimensions permanently removes them from the drawing.1. Select the added dimension(s) you wish to permanently delete from the drawing.
2. Right-click and select Delete on the shortcut menu, or on the Annotate tab, in the Delete group, click Delete. The dimension is deleted.