Back to
The Front Page
People

HOW THE WORLD RANKING LIST CALCULATES RANKINGS


John Smith plays Mark Jones in the Canary Islands Open, a class 6 event. Let's see how a single game affects each player's individual ranking.

On the World Ranking List, Smith's grade is 2200, and Jones's grade is 2100. In the internal system of the list, Smith's index is 120 and Jone's is 110.

Smith's Index = (2200-1000)/10 = 120
Jones' Index = (2100-1000)/10 = 110

Using the following formula, we calculate the delta which will be different depending on who wins.

Keeping in mind that "diff" in the formula above is the winning player's index minus the loosing player's index, if Smith Wins, the delta is 2.32 ...

but if Jones Wins, the delta is 3.68.


So,

if Smith wins the match the players new indices are as follows

Smith's new index: 120 + 2.32 = 122.32 ... and
Jones' new index: 110 -2.32 = 107.68

Their new internal grades are calculated using

New internal grade = (0.9 * old internal grade) + (0.1 * new index)

So

Smith's new internal grade: (120 * 0.9) + (122.32 * 0.1) = 120.232
Jones' new internal grade: (110 * 0.9) + (107.68 * 0.1) = 109.768

In order to get the published grade we must multiply the internal grade by 10 and add 1000.

So,

Smith's new published grade = (120.232 * 10) + 1000 = 2202.32 ... 2202
Jones' new published grade = (109.768 * 10) + 1000 = 2097.68 ... 2098

But if Jones wins the match, the players' new Grades are calculated as follows:

Smith's new index: 120 - 3.68 = 116.32 and
Jones' new index: 110 + 3.68 = 113.68

Their new internal grades are:

Smith's new internal grade: (120 * 0.9) + (116.32 * 0.1) = 119.632
Jones' new internal grade: (110 * 0.9) + (113.68 * 0.1) = 110.368

So their published grades are:

Smith's new published grade = (119.632 * 10) + 1000 = 2196.32 ... 2196
Jones' new published grade = (110.368 * 10) + 1000 = 2103.68 ... 2104

If the players were to play a second match after Jones' win then the calculations for Smith are performed using an old index of 116.32 and an old internal grade of 119.632

That's all there is to it. Now you can calculate your own WCF ranking after your important high-level international rules tournaments.


 
Back to Top   Copyright © 1996-2017 Croquet World Online Magazine. All rights reserved.