Using a 45-centimeter cubit, the Genesis dimensions make Noah's Ark approximately 135 meters long. Genesis 6:15 gives the Ark's length as 300 cubits, so multiplying 300 by 0.45 meters produces 135 meters.
The same verse gives a width of 50 cubits and a height of 30 cubits. At the same assumed cubit length, those measurements are about 22.5 meters wide and 13.5 meters high. The cubit was an ancient unit based broadly on the length of an arm or forearm, so its exact value was not universal.
For that reason, modern conversions are estimates rather than measurements of a surviving vessel. The Hebrew text supplies cubits, not meters, and scholars have proposed different cubit lengths. The 135-meter figure is a transparent conversion based on the stated 45-centimeter assumption.