Which Genesis chapter gives the main measurements for Noah's Ark?

Genesis 6 gives the main measurements for Noah's Ark. In that chapter, God instructs Noah to build a vessel 300 cubits long, 50 cubits wide, and 30 cubits high.

Genesis 6 also provides several construction details: the Ark is to contain rooms, include a side door, have a roof, and be coated with pitch. The flood itself continues into later chapters, especially Genesis 7 and Genesis 8, while the covenant and rainbow appear in Genesis 9.

This chapter-based division explains why different answers sometimes seem plausible in quizzes. Genesis 7 describes the rain and the entry into the Ark; Genesis 8 describes the recession of the waters and the birds; Genesis 9 describes the covenant. For the dimensions and core building instructions, Genesis 6 is the precise chapter.