The average American watched 31 hours of television per week in the third quarter of 2009 according to the latest Nielsen Three Screen Report.

The report by the American ratings measurement giant is a quarterly analysis of how how much time the average American spends in a typical week with TV, Internet and mobile devices.

Overall, Nielsen reports that 282 million Americans were reached by television in a month compared to 160 million who logged onto the Internet. Of those 160 million Internet users, 120 million watched video on the internet at some point during the month. Of the 225 million Americans who used a mobile phone during the month, just over 10 million watched a video on their phone.

In addition to watching TV 31 hours per week of television, the average American spent 31 minutes a week in playback mode with their digital video recorder (DVR), 4 hours on the internet, 22 minutes watching online video and 3 minutes watching mobile video.

The time with the DVR and online video was up 21.1% and 34.9% in the third quarter of 2009 when compared to the same quarter a year earlier. Despite the increases, the report found that almost 99% of video content watched in America is still done on traditional television

“Americans today have an insatiable appetite for not only content, but also choice,” says Nic Covey, director of cross-platform insights at Nielsen. “Across all age groups, we see consumers adding the Internet and mobile devices to their media diet — consuming media anytime and anywhere possible.”

Download Nielsen’s A2/M2™ Three Screen Report (.pdf file)