Home Postcode finder SA Hardwicke Bay Hardwicke Bay postcode SA Hardwicke Bay is a locality in South Australia covered by postcode 5575. Postcode 5575 State or territory South Australia (SA) Region Sa Subs Near 1 Add a free Hardwicke Bay business listing Be the first listing in Hardwicke Bay Common questionsWhat is the postcode for Hardwicke Bay?Hardwicke Bay, SA has the postcode 5575.What state is Hardwicke Bay in?Hardwicke Bay is in South Australia (SA).Does postcode 5575 cover more than one suburb?Yes. Postcode 5575 covers 17 localities, so the postcode alone does not identify Hardwicke Bay. Browse other postcodes in South Australia, or widen the search to every Australian postcode.