How to counter Hecarim
Let us take a look on how to beat Hecarim. We will look at champions who are strong against Hecarim and who are weak against Hecarim. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Jungle champion who counters Hecarim. You can already win in champion select with the right counters for Hecarim. If you want to know how to counter Hecarim then you need to take into account the best picks vs Hecarim and the worst picks vs Hecarim. This Hecarim counter data is based on matches played by Pros on patch 13.19 and previous ones. It is important to see whether Pros counter picked Hecarim or whether they played as Hecarim.
Champions used by Pros to counter pick Hecarim
Looking at the matches from Pros (see table Pros counter picked Hecarim) we can see that they picked 
Jarvan IV most often to counter pick Hecarim. The matchup Jarvan IV vs Hecarim occured 25 times. Hecarim has 13 wins and 12 losses in this matchup. Learn how to counter pick Jarvan IV to get another perspective on the data.
Lane outcome for Hecarim
When looking at Hecarim 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 Hecarim. The lane outcome of Hecarim consists of three outcomes: Win, Loss or Draw. Let's take a look of Hecarim 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 Hecarim.
Conclusion
Analyze the available data and learn how to beat Hecarim. To master Hecarim take also a look on Hecarim builds and runes for Hecarim. Good luck, Summoner!