The northern circuit's parks are spread out and the roads are long, so a little planning goes a long way. As a rule of thumb:
2 to 3 days - a taste
Enough for Tarangire and Ngorongoro, or Lake Manyara and the crater. You will see a lot, but spend real time driving. Perfect if you are also climbing or heading to the coast.
4 to 5 days - the classic
Add the Serengeti and you have the definitive northern safari: Tarangire or Manyara, the Serengeti, and Ngorongoro on the way back.
6 to 7 days - in depth
More time in the Serengeti to follow the migration, at a relaxed pace, with better chances at the big cats.
8 to 10+ days
Room to add a flight to the remote south or west, a Kilimanjaro climb, or a beach finish in Zanzibar.
Flying between parks saves hours if your time is tight. Whatever the length, we suggest arriving a night early at the hotel to rest before the pre-dawn start - and a night after to shower, repack and unwind before flying home.