Map size:
Folded: 11*6 inch
Open:11*51 inch
The Marauder’s Map was a magical document that revealed all of Hogwarts School of Witchcraft and Wizardry. Not only did it show every classroom, every hallway, and every corner of the castle, but it also showed every inch of the grounds, as well as all the secret passages that were hidden within its walls and the location of every person in the grounds, portrayed by a dot.
It was also capable of accurately identifying each person, and was not fooled by animagi, Polyjuice Potions, or Invisibility Cloaks; even the Hogwarts ghosts or Peeves were not exempt. Nor were animals, such as the caretakers cat.
One of the map’s possible flaws was that it did not differentiate people who had matching names (if a son was named after his father, the names were not given a Junior or Senior at the end). Also, it did not seem to show unplottable rooms, as it was Dobby and not the map that revealed the existence and location of the Room of Requirement.
The Chamber of Secrets never appeared on the map either because the creators never knew of it or it was unplottable as well, since when Ron and Hermione were in it collecting basilisk fangs, they did not appear on the map similar to the Room of Requirement.