In the Genesis account of Noah’s Ark, God prescribed a length of 300 cubits.
Genesis 6:15 gives the ark’s dimensions as 300 cubits long, 50 cubits wide, and 30 cubits high. The cubit was an ancient unit based broadly on the length of a forearm, so its exact modern equivalent is uncertain. Depending on the cubit standard used, the ark would have been roughly 135 to 150 metres long.
The dimensions are often discussed in relation to the ark’s unusual proportions. Its length-to-width ratio was 6:1, a shape associated with stability rather than speed. The text also says the vessel had three decks and a roof or covering. These measurements belong to the biblical narrative and should not be confused with later artistic reconstructions, which vary considerably in size and design.