First enable the "Share my Google Analytics data with Google products only" from within your Google Analytics data sharing settings page.
Google Ad Planner help you to
* Define audiences by demographics and interests.
* Search for websites relevant to your audience.
* Access aggregated statistics on the number of unique visitors, page views, and other data for millions of websites from over 40 countries.
* Create lists of websites where youd like to advertise and store them in a media plan.
* Generate aggregated website statistics for your media plan.