What was the biblical Ark’s length in cubits?

The biblical Ark was 300 cubits long.

Genesis 6:15 gives the Ark’s dimensions as 300 cubits in length, 50 cubits in width, and 30 cubits in height. The length is therefore the standard answer when a question asks for the Ark’s size in cubits.

A cubit was an ancient unit based broadly on the length of a forearm, but its exact value varied by culture and period. For that reason, the Bible’s measurement cannot be converted into one universally certain modern figure. Depending on the cubit used, 300 cubits is often estimated at roughly 135 to 150 metres.

The proportions—six times as long as it was wide and ten times as long as it was high—have attracted engineering discussions. Genesis describes a large, boxlike vessel rather than a ship designed for speed or navigation. The account emphasizes survival through the waters, and it says the Ark had rooms, a roof, and an opening or window.