I cannot understand how the ratings are calculated.

I just finished a game of online chess.  Before I resigned, my rating was 1280 and my opponent's was 1300.  After I resigned, my rating was 1273 (as I would expect) but his was 1315, an increase of 15 points for beating an opponent with a lower rating.  Does this make any sense at all?

There are many factors at work in addition to your rating, your opponents rating, and the result.

There is also something called the RD (Ratings Deviation).  In a way, it is a measure of the accuracy of the rating, and each of you have one.  The RD is adjusted up or down with every game, but it also slowly climbs up in between games (older ratings are considered less accurate).

So your rating changes based also on your RD and your opponent's RD.  If your RD is high (inaccurate), then your rating will swing a little more wildly until the RD goes down.  If your opponent's RD is high, then your rating will change less so that you do not get unduly rewarded or punished for playing someone with an inaccurate rating.

Some light reading for you on how chess.com ratings are arrived at:

http://www.glicko.net/glicko/glicko.pdf

No.

Absolutely: Your Glicko RD is 42, while your opponent's Glicko RD is 78.

Thanks, everyone, for your comments.  @Rsava: I don't know what you would call "heavy" reading , but I'll admit I know a bit more now than I did before.  There's certainly a lot more to ratings than I thought there was!

Thanks again to all!

Yes, it's indeed not some erratic number forged by chess.com, but a serious statistical measure devoloped over many years by respectable scientists.

An example of some of my "heavy reading":

http://calvinhobbesdaily.tumblr.com/ 

Cooool.

So where do I lookup my rd? And the lower number means a more accurate rating, right?

You can see your RD on the full stats page: http://www.chess.com/echess/stats/MrDamonSmith

Yours is currently 105.  Mine is 54.  The lower the RD, the more accurate the rating is considered to be.

Basically, the RD means that there is a high level of confidence that your "true" rating (a mystical value that is unknown to all) is within the RD value of your "performance" rating (the rating based off of your performance in all rated games).

For you: Your "true" rating is likely to be somewhere in the range of 1915 to 2125 (2020 plus or minus 105)

For me: My "true" rating is likely to be somewhere in the range of 1621 to 1729 (1675 plus or minus 54)

If you know anything about statistics, I believe the RD is related to the Standard Deviation.

The answers above are all accurate. So as a summary:

1. RD gets lower the more frequently you play, so if you play a ton of rated games in a short time you will have a lower RD meaning your rating gets less change. (FYI my rating jumped almost 300 points in 2 tourneys because of my high RD) :)

2. you get points for winning consecutive matches. Eg:

R1 Win 1500  R2 Win 1500. Let's say you get 15 points for your first win. Then you would get bonus points (let's say 7) so your gain for second round is 22. BTW your number of bonus points increase per extra consecutive game, so let's say

R1 Win 1500 R2 Win 1500 R3 win 1450. Then you get (let's say +15 R1 +22 R2 and R3 +15 + 12 bonus = +27.)

Thanks y'all. Now I know about rd. Had seen it of course but never made effort to find out what it meant or how it worked.

In 21 october 2014 i have rating in standart chess - 1639.

In 26 october 2014  i played next game and my rating - 1939.

Help!

@Sindbad:

http://www.chess.com/forum/view/livechess/standard-ratings-boost

@ baddogno

Thanks!