How long before departure time do i have to be in the Sydney airport for an international flight ?

A: It's 3 hours on most International flights. We just returned home from a holiday in California, and we needed to check in 3 hours prior to leaving Sydney, and the same coming back from San Francisco. Even with the 3 hours, we almost missed our flight due to a hold up in customs, so I would try to get there as early as possible, just in case.