According to Genesis, Noah's Ark was 30 cubits high.
Genesis 6:15 gives the vessel's three principal dimensions: 300 cubits long, 50 cubits wide, and 30 cubits high. The height is the smallest of those figures, but it is still part of the same formal specification that describes the Ark's construction.
Genesis also says the Ark had lower, middle, and upper decks. Those decks, together with the stated height, indicate a substantial multi-level vessel in the narrative, although the text does not provide exact deck spacing or a complete engineering plan.
The ancient cubit was not identical everywhere, so converting 30 cubits into modern units involves uncertainty. Depending on the cubit used, estimates differ. The biblical number itself is stable: 30 cubits, not 30 meters or 30 feet.