In the biblical Noah’s Ark account, Genesis gives the ark’s length as 300 cubits.
Genesis 6:15 lists three dimensions for the vessel: 300 cubits long, 50 cubits wide, and 30 cubits high. The text does not define the exact length of a cubit, so modern estimates vary. Using a common ancient measure of about 45 centimetres, 300 cubits would be roughly 135 metres, or 450 feet.
The dimensions are important because they are unusually precise for a short ancient narrative. They describe a long, box-like vessel rather than a conventional ship designed for speed or navigation. Genesis says the ark was divided into compartments and coated with pitch to make it watertight.
A common mix-up is to treat 300 cubits as the ark’s height or width. Those figures are 30 and 50 cubits respectively. The same measurements are also discussed in comparisons between the Genesis account and other ancient flood traditions.