Albert Barnes Commentary 1 Kings 6:31

"And for the entrance of the oracle he made doors of olive-wood: the lintel [and] door-posts were a fifth part [of the wall]." — 1 Kings 6:31 (ASV)

A fifth part — This translation is better than the one provided in the margin. The meaning seems to be that the lintel was one-fifth of the wall's width, and each doorpost was one-fifth of its height. Thus, the opening was a square of four cubits, or about six feet.