How do I dimension a circle or arc?

Diameter of a circle#

1. Choose Dimension and click the circle line (not the centre).
2. Move the pointer: the dimension line rotates along, the text follows the pointer — also inside the circle.
3. Click. The dimension shows ⌀ and the value; Edit dimension opens.

Radius of an arc#

1. Click the arc with Dimension. The point you hit sets the starting angle of the arrow.
2. Pull the text to the desired spot and click. The dimension shows R and the value. The arrow follows the pointer around the centre — even beyond the ends of the arc; an auxiliary dimension arc is then created. Shift keeps the arrow at the angle of the first click.

A circle is dimensioned as diameter, an arc as radius. To switch, open Edit dimension (double-click) and click R → ⌀ or ⌀ → R. Arrow: inside/outside puts the arrow on the other side; for a radius outside hides the line to the centre.

Arc length#

1. Choose Arc length dimension in the list of the Annotate group.
2. Click the arc and pull the dimension arc outwards.
3. Click. The dimension shows ⌒ and the arc length; it stays driven.