I didn't go look at the page that was pointed out, but here's a quickie:
(numbers vary on nationality, type of squad, and for WW2, year of the war)
squad: 6 to 15 men, or 1 vehicle
section: 2 squads
platoon: 2 to 5 squads (figure around 40 men)
company: 3 or 4 platoons usually (figure around 100 men)
battalion: 2 to 5 companies, but since different types of companies were involved, size estimate is odd
Up from there, it goes brigade/regiment, then division.
Hope that helps!
John
(first posting, but I've been lurking a few days)