Genesis gives Noah’s Ark a length of 300 cubits.
Genesis 6:15 lists the vessel’s dimensions as 300 cubits long, 50 cubits wide, and 30 cubits high. A cubit was an ancient unit based roughly on the length of a forearm, but its exact value varied by culture and period.
Using a commonly estimated cubit of about 45 centimeters, 300 cubits would be approximately 135 meters, or about 450 feet. That conversion is an estimate, not a measurement stated by Genesis itself.
The proportions are roughly 6:1 in length to width, which has often prompted comparisons with stable barge-like vessels. Such comparisons concern the dimensions described in the text; they do not establish that the Ark has been found or that the account is an engineering specification in the modern sense.