Senators are elected by a preferential voting system known as proportional representation.

Candidates for the Senate stand for a state or territory. It is a Constitutional requirement that each state be equally represented regardless of its population.

There are a total of 76 Senators: 12 for each state and two for each territory. Senators for each state are elected for a six year term. Senators for each territory are elected for a term equivalent to the duration of the House of Representatives. When a House of Representatives and half Senate election are held at the same time, 40 Senate vacancies are contested.

When a Double Dissolution is declared, as there was in 1987 and 2016, all 76 Senate positions are made vacant.