How many days should you spend in Sydney?
Give Sydney enough time for the harbour, beaches, ferries, neighbourhoods and one slower day. Treat it as a quick arrival city and you miss the part where the place starts to breathe.
Answer
Three days can cover the obvious city shape; four or five lets Sydney feel like more than icons. The city works through movement: ferries crossing the harbour, coastal walks, a swim, a neighbourhood dinner, a museum or market, and a slower day where the weather decides the plan. If you also want the Blue Mountains, build that in rather than stealing it from Sydney itself. The mistake is landing, ticking the Opera House and leaving before the harbour rhythm has done its work.