In August (2009) Google launched their Adwords Bid Simulator tool to help users determine their optimum bidding strategies. The tool takes some of the guess work out of cost per click (CPC) bidding by estimating the number of clicks or impressions you could have received if you had used a different maximum CPC bid.

To give you a better understanding of how you can use this tool to your advantage watch the video below.

source:  The Official Blog