The jazz station previously only broadcasted on DAB in London, the North West and the West Midlands.
Its weekly reach is 448,000 listeners, according to the most recent Rajar radio listening figures, covering the fourth quarter of 2010, while its listeners consume 4.2 hours of output, on average.
Jazz FM originally launched in 1990 as a station for London. It was acquired by Guardian Media Group in 2002 and is now under the ownership of Richard Wheatly, who was its chief executive during the 1990s.
It re-launched as a digital-only station in October 2008 under licence from Guardian Media Group.
Earlier this month its restructured its sales team, promoting head of client development Jo Coltman to director of sales.