To measure performance of my twitter hashtag campaigns, Trackmyhashtag is the best tool in my experience and trustworthy. It provides an extensive access to a wide variety of analytics to show how our chosen hashtags are performing.
Trackmyhashtag provides various statistics :
1. The reach, impressions and engagement of any hashtag
2. Tweet timeline analytics with daily and weekly pattern
3. Provide top list of influencers related to a hashtag
4. Most liked and retweeted tweets,top related media, Hashtag and URL related to a hashtag
5. Predictive analytics include best time to post and best hashtag to use
6. Competition analysis helps to make strategies
7. Other metrics such as top languages, geographical presentation , device source
This tool provides a free trial for 5 days and the premium features are also affordable. You should use this tool yourself and see how much you will like it.