There is no official rating. But is most likely a PG-13 rating
Transformers: Dark of the Moon (2011) is rated PG-13.
NO IT IS RATED PG-13!!
Transformers 2 has been rated as a 3 star movie
3 stars
Transformers - 1984 The Immobilizer 2-2 is rated/received certificates of: Australia:G
yes its rated PG-13
Transformers - 1984 Masquerade 2-42 is rated/received certificates of: Australia:G
Transformers - 1984 The Gambler 2-31 is rated/received certificates of: Australia:G
Transformers - 1984 The Core 2-24 is rated/received certificates of: Australia:G
Transformers - 1984 Microbots 2-11 is rated/received certificates of: Australia:G
Transformers - 1984 Traitor 2-5 is rated/received certificates of: Australia:G
Based on the fact that all of the past Transformers movies have been rated PG-13 I doubt that this one will be rated differently. Even though the new movie does look more violent I doubt the rating will be effected.