My last 50 Tweets have reached almost 14,000 people thanks to RTs and @replies from people in my network.

TweetReach calculates the reach of tweets as they ripple through a network. The online application calculates impressions and the people in your network that push your tweets out.

A full report that contains all mentions of any search term over the past seven days or up to 1500 results cost $20.

(via @jangles, @DavidBrain and @MarkPinsent).