It happens sometimes: you're wondering which hashtag to use on Twitter for your next tweet—which one is most used and likely to have the greatest reach among several similar or related ones—and since you don't have pre-monitoring enabled, you lack the data to make a decision.
Here are six tools whose free version lets you compare hashtags you're unsure special lead about and get a quick, rough analysis of their impact (plus additional information).
1. Social Bearing
Analyzes the impact of the hashtag based on the time period determined by the tool (at least the last two minutes). It calculates reach, impressions, total RTs and favorites, and displays the most recent 100 posts. It also assigns a sentiment (very good, good, neutral, bad, terrible) and identifies the 10 users who use it the most, the 10 users with the greatest reach and influence, the 10 most frequently used words in tweets, and the 10 most frequently used complementary hashtags. Tweets can be filtered by language and content type (image, link, reply, mention, etc.).
SocialBearing
2. Rite Tag
Compare hashtags related to the topic based on a specific hashtag. For each hashtag, it shows the number of tweets sent, retweets, potential views per hour, and the percentage of tweets with images and links. A color-coded legend also indicates the frequency of use for each hashtag.