2Condit, Tom, and Brian Lacy. The Beltany Stone Circle. Bray: Archaeology Ireland. Heritage Guide No. 4 (1998).
Only Lough Gur's Grange Stone Circle is larger; 46m v. 45m in diameter.
While most sources count 64 stones in the circle, a 1988 journal article refers to 65 stones. (Van Hoek, M.A.M. "The Prehistoric Rock Art of Co. Donegal (Part II)." Ulster Journal of Archaeology Third 51 (1988): 25.)
While most of the stone circles in Ireland are thought to have been constructed from c. 2100 BCE to 700 BCE, new data indicates that the Beltany Stone Circle may have been constructed as early as 3,000 BCE. See the reference to the “Rediscovering an Ancient Landscape" conference in Raphoe.