How to counter Rammus
Let us take a look on how to beat Rammus. We will look at champions who are strong against Rammus and who are weak against Rammus. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Jungle champion who counters Rammus. You can already win in champion select with the right counters for Rammus. If you want to know how to counter Rammus then you need to take into account the best picks vs Rammus and the worst picks vs Rammus. This Rammus counter data is based on matches played by Pros on patch 14.23 and previous ones. It is important to see whether Pros counter picked Rammus or whether they played as Rammus.
Champions used by Pros to counter pick Rammus
Looking at the matches from Pros (see table Pros counter picked Rammus) we can see that they picked 
Lee Sin most often to counter pick Rammus. The matchup Lee Sin vs Rammus occured 4 times. Rammus has 3 wins and 1 losses in this matchup. Learn how to counter pick Lee Sin to get another perspective on the data.
Lane outcome for Rammus
When looking at Rammus counters you will notice that win rates alone are not conclusional. Therefore we provide an overview (see table Lane Outcome) where you can see the lane outcome of Pros who played Rammus. The lane outcome of Rammus consists of three outcomes: Win, Loss or Draw. Let's take a look of Rammus lane and match outcome for specific matchups. Considering the lane outcome and the match outcome of a specific matchup, might enable you to find the right counter for Rammus.
Conclusion
Analyze the available data and learn how to beat Rammus. To master Rammus take also a look on Rammus builds and runes for Rammus. Good luck, Summoner!