Calum Thomas Hood (born 25 January 1996) is an Australian musician, known for being the bassist and the backup vocalist of the pop rock band 5 Seconds of Summer. Since 2014, 5 Seconds of Summer have sold more than 10 million albums, sold over 2 million concert tickets worldwide, and the band's songs streams surpass 7 billion, making them one of the most successful Australian musical exports in history.