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1. 03 Jan '08 01:46 / 20 edits
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New Rating = Old Rating + K * (Score – Win Expectancy)
K is a constant (32 for 0-2099, 24 for 2100-2399, 16 for 2400 and above)
Score is 1 for a win, 0.5 for a draw and 0 for a loss.

The Win Expectancy is calculated using the following formula:
Win Expectancy = 1 / (10^((OpponentRating-YourRating)/400)+1)

For more, see FAQ

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Explanation of Symbols
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Rating Difference – The difference in rating between you and your opponent at the conclusion of the game
HR(W)– Higher rated player wins said points
HR (L) – Higher rated player losses said points
LR (W) – Lower rated player wins said points
LR (L) – Lower rated player losses said points
Game Drawn – Game is drawn. Higher rated player losses said points / Lower rated player gains said points

Example(1):

Opponents rating: 1415

Status: You win!

Your rating falls between 0 and 2099. The difference between you and your opponent’s rating is 1415-1400 = 15, you are the player with the lower rating. 15 falls between 11-32 therefore you gain the points in the “Lower Player” Column for the number, 17.

Example (2):

Opponent's Rating: 1800

Status: Game Drawn

Your rating falls between 2100 and 2399. The difference between you and your opponent’s rating is 2200-1800 = 400, you are the player with the higher rating. 400 falls between 365-428 therefore you lose the points in the "Game Drawn" Column, 10.

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Rating Calculations [0-2099]
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Rating_______HR(W)____Game___HR(L)
Difference____LR(L)____Drawn____LR(W)
0 - 10 ________ 16 ______ 0 ______ 16
11 - 32 _______ 15 ______ 1 ______ 17
33 - 54 _______ 14 ______ 2 ______ 18
55 - 77 _______ 13 ______ 3 ______ 19
78 - 100 ______ 12 ______ 4 ______ 20
101 - 124 _____ 11 ______ 5 ______ 21
125 - 149 _____ 10 ______ 6 ______ 22
150 - 176 _____ 9 _______ 7 ______ 23
177 - 205 _____ 8 _______ 8 ______ 24
206 - 237 _____ 7 _______ 9 ______ 25
238 - 273 _____ 6 ______ 10 ______ 26
274 - 314 _____ 5 ______ 11 ______ 27
315 - 364 _____ 4 ______ 12 ______ 28
365 - 428 _____ 3 ______ 13 ______ 29
429 - 523 _____ 2 ______ 14 ______ 30
524 - 719 _____ 1 ______ 15 ______ 31
720 + _________ 0 ______ 16 ______ 32

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Rating Calculations [2100-2399]
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Rating_______HR(W)____Game___HR(L)
Difference____LR(L)____Drawn____LR(W)
0 - 10 ________ 12 ______ 0 ______ 12
11 - 32 _______ 11 ______ 1 ______ 13
33 - 54 _______ 11 ______ 2 ______ 14
55 - 77 _______ 10 ______ 3 ______ 14
78 - 100 ______ 9 _______ 3 ______ 15
101 - 124 _____ 8 _______ 4 ______ 16
125 - 149 _____ 8 _______ 5 ______ 17
150 - 176 _____ 7 _______ 5 ______ 17
177 - 205 _____ 6 _______ 6 ______ 18
206 - 237 _____ 5 _______ 7 ______ 19
238 - 273 _____ 5 _______ 8 ______ 20
274 - 314 _____ 4 _______ 8 ______ 20
315 - 364 _____ 3 _______ 9 ______ 21
365 - 428 _____ 3 ______ 10 ______ 22
429 - 523 _____ 2 ______ 11 ______ 23
524 - 719 _____ 1 ______ 11 ______ 23
720 + _________ 0 ______ 12 ______ 24

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Rating Calculations [2400+]
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Rating_______HR(W)____Game___HR(L)
Difference____LR(L)____Drawn____LR(W)
0 - 10 ________ 8 _______ 0 ______ 8
11 - 32 _______ 8 _______ 1 ______ 9
33 - 54 _______ 7 _______ 1 ______ 9
55 - 77 _______ 7 _______ 2 ______ 10
78 - 100 ______ 6 _______ 2 ______ 10
101 - 124 _____ 6 _______ 3 ______ 11
125 - 149 _____ 5 _______ 3 ______ 11
150 - 176 _____ 5 _______ 4 ______ 12
177 - 205 _____ 4 _______ 4 ______ 12
206 - 237 _____ 4 _______ 5 ______ 13
238 - 273 _____ 3 _______ 5 ______ 13
274 - 314 _____ 3 _______ 6 ______ 14
315 - 364 _____ 2 _______ 6 ______ 14
365 - 428 _____ 2 _______ 7 ______ 15
429 - 523 _____ 1 _______ 7 ______ 15
524 - 719 _____ 1 _______ 8 ______ 16
720 + _________ 0 _______ 8 ______ 16

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Assumptions
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These charts work on the assumption that decimals greater than or equal to .5 are rounded up in all circumstances.

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I am sure there are both mathematical
any out that you may find.

Drew
2. 03 Jan '08 03:52
Wow, it must've taken forever to post that- Thanks for the info, I'll bookmark this page incase I ever need to refer to it again
3. 03 Jan '08 04:04
Originally posted by chesskid001
Wow, it must've taken forever to post that- Thanks for the info, I'll bookmark this page incase I ever need to refer to it again
It could have been copied and pasted from somewhere, but who knows.

Anyway I have a question, how can you calculate your rating if you don't have a rating?
4. 03 Jan '08 07:27 / 1 edit
Your provisional rating will sort itself out as soon as you have completed 20 rated games. Looking at the opponent ratings in your graph I would expect your rating to come out somewhat higher than it is at present. In any case it takes quite a lot of games before your rating here will stabilise - and remember it's a correspondence chess rating, often quite different from your OTB rating.

And thanks again Drew for re-posting these charts; I keep a copy of one taped to my screen - and people think I'm clever because I can tell them how much it's going to cost them to lose this game ....
5. 03 Jan '08 07:41
It also goes to show that it sucks to be higher rated. You have to work so hard and still get less points.
6. 03 Jan '08 20:46
Originally posted by Tyrannosauruschex
It also goes to show that it sucks to be higher rated. You have to work so hard and still get less points.
But it sucks even more to be lower rated (for different reasons, of course).