Arc Fit

The Arc Fit tool will replace any line, polyline, spline, or Bezier curve with a best fit arc.

Select the Arc Fit tool on the ribbon or press Shift + F. Any elements that are not allowed for this tool will be dimmed.

Mouse over an element. You will see a preview of an arc that best fits the points of the original element. Click the element to accept the replacement. You can also marque select multiple elements. Left click, drag the marque, and release. Elements will be previewed as you drag. When you release the new elements will be created.