According to Genesis, the window Noah made in the Ark was one cubit high.
Genesis 6:16 describes the ark’s construction and says Noah should finish it “to a cubit” above. English translations vary slightly in how they phrase this passage, but the traditional reading treats the window or opening as one cubit in height.
The verse also specifies a door in the side of the ark and three decks. These details make the account more than a simple statement that Noah built a boat: Genesis provides a compact set of architectural instructions, including dimensions, compartments, an opening, and a door.
The cubit itself was an ancient unit based broadly on the length of a forearm, so its modern equivalent is not exact. That uncertainty affects physical reconstructions, but not the biblical number. The canonical measurement in the text is one cubit.