In Genesis, Noah’s Ark was instructed to be 300 cubits long.
Genesis 6:15 gives the ark’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 is roughly 135 metres, or 450 feet.
The measurements describe a large rectangular vessel rather than a conventional modern ship with a pointed bow. Genesis also says that the ark had rooms, a roof, and three levels. The text does not provide a complete naval blueprint, so reconstructions differ in details such as the shape of the hull and the precise length of a cubit.
The length is sometimes confused with the ark’s width or height. The key numerical pattern is 300 by 50 by 30 cubits, making the length ten times its height and six times its width.