How high did the Floodwaters rise above the mountains in Genesis?

Genesis says the Floodwaters rose fifteen cubits above the mountains. Genesis 7:20 uses this figure after describing the waters covering the high mountains under the heavens.

A cubit was an ancient measurement traditionally based roughly on the length of a forearm, but its exact historical value varied. Because Genesis does not define the cubit in modern units, fifteen cubits cannot be converted into one universally certain metric or imperial number. Depending on the cubit used, it is often estimated at several metres.

The verse is part of the biblical narrative’s description of complete inundation. It follows the statement that the waters increased and lifted the Ark above the earth. The number should not be confused with the Ark’s height, which Genesis gives as thirty cubits, or its length, which is three hundred cubits.

Readers also sometimes confuse fifteen cubits with the 150 days during which the waters prevailed. One is a height; the other is a duration.