From http://blog.dota2.com/2013/12/matchmaking/Wishy wrote:
I must say this ranked matchmaking actually seems to be working, time to play again. What's a decent rating? I've seen some pros around 5.8k~6k but no idea what's high or low.
5% 1100This means if you have 3200 rating you are better than 90% of all players (accounts).
10% 1500
25% 2000
50% 2250
75% 2731
90% 3200
95% 3900
99% 4100
This is for normal matchmaking though, for ranked all numbers should be a bit higher.