Use the SmartDimension command to create Dimensions by specifying entities.
You can apply the command to Lines, PolyLine segments, Arcs, Circles, and Rings:
If you select a Dimension in the graphics area and the ribbon is active, the corresponding Dimension Selection contextual ribbon tab appears. The contextual ribbon tab groups options and tools for controlling the DimensionStyle, arrows, and dimension lines.
To dimension entities:
To use another dimension type for Circles or Arcs, specify an option:
Note: The chosen option is the default the next time you use the SmartDimension command.
When you move the pointer during a linear dimensioning, you can:
Use the ContinueDimension command to create linear dimension chains.
Access
Command: SmartDimension
Menu: Dimension > Smart
Ribbon: Annotate > Dimensions > Smart