The Gullet in Westeros is a stretch of water , not a creature or structure, so it does not have a fixed “size” in the usual sense. It sits between Dragonstone and Driftmark to the north and Massey’s Hook to the south, connecting Blackwater Bay with the Narrow Sea.

What that means

  • It is best understood as a narrow maritime channel or strait.
  • The lore sources describe its location and importance, but they do not give exact measurements like width or length.
  • In story terms, it matters because it is a naval chokepoint, especially during the Battle of the Gullet.

Simple version

If you mean “how large is it on the map,” the answer is: large enough to be a major sea lane, but not precisely measured in canon.

TL;DR: The Gullet is a narrow strait , and Westeros lore does not provide an exact numeric size for it.