Twitter is a great tool to expand the reach of your message beyond your website, enewsletter or blog. But you can’t measure your reach solely by the number of followers you have—you have to look beyond and consider the user who follows your followers.

With Twitter comes to ability to “retweet” something that one of the users you follow has posted. Think about it: If you tweet something to your 200 followers, 200 people receive your message. But if it’s a tweet that, say, half of your followers find interesting or valuable enough to retweet, you have also just reached all of the people following those 100 followers of yours. And if those people retweet you, too, you reach their followers as well. The math can get huge, and your reach can grow exponentially.
One of the main reasons users follow other users on Twitter is because they want to read what those users have to say, whether they know them or not. While there are spammy users who simply parrot what other Twitter users have tweeted, for the most part a retweet indicates a vote that the certain tweet is important.
Measuring your reach
There are plenty of online tools claiming the ability to quantify your reach on Twitter, but it’s not an exact science. You can use services like TweetReach or Twinfluence to determine how many people you might be reaching with a specific tweet, but they don’t take into account aspects like who retweets you, users who might be filtering out certain words or phrases from their stream, or those who follow so many Twitter users that they cannot possible read every tweet that comes across their stream in a day.
The quality of your followers
While it’s always fun to get notifications that someone new is following you, you’ve got to keep an eye on how many followers are actually “real.” Spammers or bots following you on Twitter can hurt your credibility or value as a Twitter user if you allow enough of them to build up on your list. Imagine stumbling upon a profile you think looks interesting but discovering that 60 percent of its followers are obvious spam profiles. It might make you question the original user’s purpose for using Twitter, and also why they aren’t paying much attention to their account.
There aren’t any steadfast rules, per se, for Twitter—just keep in mind that it’s a communication tool. If you do a good job participating in the conversation and build a good list of followers who do the same, the reach of your content will continue to grow.