Click the Dimension Tool
in the toolbox or CTRL+0 (zero).
Click the Aligned, Horizontal, Vertical, Angular, or Radial button in the ribbon.
Move the pointer to the starting point of the object you want to measure, and press and hold the left mouse button. Use dynamic snap points to link to an object.
Drag the pointer to the endpoint of the object you want to measure and release the mouse button. You can use CTRL to constrain the angle to increments of 15 degrees. A dimension line appears between the two points. The blue handle at the cursor location indicates the position of the dimension text.
Move the mouse in the appropriate direction to offset the dimension line and to adjust the location of the dimension units. You can use SHIFT to force the alignment point to the center.
After positioning the dimension line and text, click the left mouse button to finish drawing the dimension line.
If you make a mistake while drawing a dimension line, you can press ESC to start over.
in the toolbox or CTRL+0 (zero).