In the biblical Book of Genesis, Noah’s Ark is described as 300 cubits long. Genesis 6:15 gives the vessel’s three principal dimensions as 300 cubits in length, 50 cubits in width, and 30 cubits in height.
A cubit was an ancient unit based broadly on the length of a forearm, so its exact modern equivalent is uncertain. Using common estimates, 300 cubits would be roughly 135 metres, or about 450 feet, long. The text therefore presents the ark as a very large rectangular vessel rather than a conventional sailing ship.
Readers sometimes assume the biblical measurements are given in modern feet or metres, but the original Hebrew text uses cubits. The dimensions are also distinct from the flood-boat measurements in other ancient traditions, including the Epic of Gilgamesh. Genesis focuses on the ark’s preservation of Noah, his family, and the animals rather than on navigation or cargo capacity.