The stone itself is large, roughly 3.75 metres by 2.5 metres, but the decorated portion is more intimate, around 2.2 metres by 1.2 metres, tilted toward the northeast and partially disappearing beneath the surrounding peat on its upslope side. What survives above ground is enough to make the effort of getting here worthwhile for anyone with an interest in prehistoric carving.

The centrepiece of the decorated surface is a cup-and-ring motif, the term for prehistoric carvings consisting of a small circular hollow, or cupmark, surrounded by one or more concentric rings pecked into the rock. At Kealduff, there are six such rings around the central cup, making it an unusually elaborate example. Two linear grooves extend outward from the cupmark; one runs east toward the outermost ring, and a second travels northeast beyond the rings entirely, terminating in a separate cupmark. Further cupmarks cluster to the west and northwest of the main motif, and lines of pickmarks extend across the surface, one of them continuing southeast under the peat. The northern half of the decorated area is noticeably smoother than the southern half, which has led to the suggestion that it may have been deliberately prepared before carving began. The sandstone shows some evidence of freeze-thaw weathering, with small sections having flaked away over time. Pre-bog walls in the vicinity hint that the landscape around the rock was once worked or settled, long before the blanket bog encroached and began to swallow both the walls and the lower edges of the outcrop itself.