In the Genesis account of Noah's Ark, the ark's length was 300 cubits. Genesis 6:15 gives three measurements for the vessel: 300 cubits long, 50 cubits wide, and 30 cubits high.
A cubit was an ancient unit based broadly on the length of a forearm, so its exact modern equivalent is uncertain. Using common estimates of about 44–52 centimetres, the ark would have been roughly 132–156 metres long. The biblical measurements therefore describe a very large rectangular vessel rather than a small boat.
Genesis says the ark was made from “gopher wood,” coated inside and outside with pitch, and divided into compartments. It also had three decks, a roof, and an opening near the top. The text does not identify gopher wood with a securely known modern tree species.
The dimensions are often compared with later shipbuilding traditions, but the account presents the ark primarily as a vessel of preservation during the flood, not as a normal sailing ship. Modern reconstructions necessarily depend on assumptions about the cubit and the timber.