Kelly Clarkson has topped a list of the biggest-earning American Idol stars.

Forbes, which put together the list based on income made in the 12 months to May 2012, ranked Kelly at the top with an eight million dollar income for the period, despite it being a decade since she won the first season of the show.

The Stronger singer, who performed at President Obama's inauguration, is at the top thanks to album sales, a mentor role on The Voice, a Toyota advert and a lucrative tour.

Carrie Underwood and Chris Daughtry both share the second spot, with estimated earnings of five million dollars each.

Scotty McCreery was next with an estimated four million dollars, while Dreamgirls star Jennifer Hudson, who didn't win the show, increased her earnings with a Weight Watchers endorsement and memoir, completing the top five with three million.

Last year's American Idol winner Phillip Phillips does not make the top 10 as his success came too late, though Forbes says that he could have a place next year.