Are you drawing and dimensioning a full circle and then trimming to create the arc?
If yes, then create the arc before dimensioning.
OMG it was as easy as that, typical.
Yes drawing dimensioning then trimming, your way gave me the result I was looking for.
Mark, I am having the same problem. Mine is calling out a diameter even though the radius was created in sketcher while making a simple rectangular pocket with fillets in the corners. This should never, ever, be called out as a diameter (Drafting 101). Solidworks should no better than to call out a diameter if the circle is not complete. I don't care how it was created.