SYNOPSIS
Basically, I saw some of the other guides on ranks and they were completely false and total BS, so I decided to make this guide. I will not guarantee that this guide is 100% accurate, but I do truly believe that it is the most detailed/accurate guide on CSGO ranks on Steam, and in this guide I point out why several common misconceptions on ranks are almost certainly false, such as the idea that kills affect rank.

I'm going to start off by making it clear that the ONLY thing that affects your rank is wins/losses/ties of ROUNDS. The Competitive Matchmaking system is based on the chess ranking system called Elo. Winning ROUNDS will always gain you Elo points, losses will always lose you points, and ties depend based on the average ranks of the two teams. Essentially, each round of a match is treated as a chess game. Before the match, the system will calculate how many rounds you are expected to win based on the average ranks of each of the two teams. After a match, the system will compare its prediction with what really happened. Kills, score, weapons used, or getting reported do not EVER affect your rank or how many Elo points you get.

Previously, I have stated that only wins/losses/ties of MATCHES affect rank. After several people have told me that they have gained rank after a loss, and a few people have shown me screenshots, I have now given new thought into how the rank system works.

I still highly doubt that individual performance plays ANY role at all in your rank, considering that it is still possible to end up on the very bottom of the scoreboard and gain rank. Furthermore, it appears that the games that are really close have a lower chance of changing your rank, considering ties or losses almost never change your rank. It would also not make sense on Valve's part to make individual performance a role in ranking, considering CS is a team-based game and considering how there are simply too many factors to account for. For example, a noob player could sneak up from behind and kill an extremely skilled player. If individual performance affected rank, the high-ranked player would theoretically lose a lot of points from getting killed by a low-ranked player. However, we know that this scenario does not accurate represent the skill levels of either player, because most likely the skilled player is fighting other enemies and the noob just happened to be at the right place at the right time. Also, even moderately skilled players with good weapons such as the AWP can easily kill an extremely skilled player, and this would not accurately reflect the skill levels of either player.

RANKS
There are 18 ranks in CSGO, the lowest of which is Silver 1 and the highest of which is Global Elite. The majority of players fall between around Silver 3 and Nova 2, with relatively few players being below Silver 3. There is a sizable population of Nova 3-4s and Master Guardians, but it is nowhere near the number of the lower Novas and high Silvers. Eagle ranks and above are rather rare and take years of practice to attain.

WINS
You ALWAYS gain points from winning rounds. However, the amount gained may be almost nothing, or it may be a great number. Winning against a team that is, on average, higher ranked than you will get you more points depending on the magnitude of the difference. Winning rounds against a lower ranked team, in converse, will give you fewer points. The amount of "rank points" you gain for a match depends based the number of rounds you win. It is therefore possible to win 7 or so games in a row and not gain rank, or win just 1 or 2 games and gain rank.

LOSSES
Losing rounds will ALWAYS lose you points, regardless of your team's average rank or the enemy team's average rank. Like I said before, however, the amount lost depends on the difference of your team's average rank and the enemy's average rank. Losing to a very high-ranked team will not lose you much points at all, while losing to a low-ranked team will lose you many points.

TIES
It is possible to gain or lose rank in the event of a tie. Getting a tie does not mean that no points are transfered between the two teams. The team with a higher average rank will lose points in the event of a tie, and the lower ranking team will gain points. The amount of points lost or gained depends on how different the average ranks are between the two teams. Two teams with the same ranks are expected to be tied.


FRIENDS
"Should I play with low-ranked friends?" It is up for you to decide. Yes, matchmaking will take into account your low-ranked friend when searching for games, so most likely there will be someone around the rank of your friend as well on the enemy team. I would suggest, however, that if they aren't going to play seriously just take them to Casual mode.

"Should I play with friends of similar ranks as mine?" It most likely will help. Playing with friends rather than randoms will greatly increase cooperation and teamwork, and on average I would say you win more playing with similarly ranked friends than with randoms.

"Should I play with high-ranked friends?" If you want to play with high-ranked friends so you can keep winning and gain rank, I would say definitely do NOT do that. You may gain rank but it would not accurately reflect your skill, and when you are playing by yourself you will find yourself frustrated by significantly more skilled players. You are also hurting your teammates, who will lose games because of you. Eventually, you will probably lose rank and return to your previous rank anyway, so why bother?

ADDITIONAL NOTES
Sometimes people complain about losing just 1 game and then decreasing rank, and then not being able to level up again even after 5 wins. If it appears that you have only lost 1 game and then lost rank, it is probably because you have lost several games a few days ago. The game does not reset your Elo points just because you haven't played in a few days (although you will have to play 10 games to regain your rank if you haven't played in a few months). Everytime you gain or lose rank, your are put back in the "middle" of the Elo point spectrum, so losing 1 or 2 games right after you gain a rank will not lower your rank again.

Let's say you start from 0 points, gain 1 point for every round win, and lose 1 point for every loss. In reality, the number of points you gain or lose is not constant and depends on the ranks of both teams, but let's just say it is for example's sake. You have to get to 10 points to raise rank, and get to -10 points to lose rank. When you gain or lose rank, your points reset to 0.

Many people also wonder if their ranks truly represent their skills. In the long term, it does. Everyone has a match every so often in which they do very well, and it is in these moments that people generally get angry for their low rank. However, they forget all the times when they perform just average, and the few times they completely screw up. These cancel out, and after playing many matches your rank will more or less reflect your CURRENT skill. That being said, however, CS is a game of practice. The lowest rank I have ever had was Silver 4, but after excruciating practice my rank had continually increased and it is now Master Guardian. Unless you already have an extremely high rank, it is almost unheard of that the more you play, the lower your rank will get, so don't be afraid to keep playing matchmaking for fear of losing your rank.

FURTHER READING
CS Official Blog Article on Ranks
Wikipedia Article on the Elo System[en.wikipedia.org]