Rn = Ro + K (W – We)
Rn New rating
Ro Old rating
K Value of a single game –30 between 20 and 40…
K = 10 if rating > 2400
K = 15 if rating under 2400
K = 25 for players new to the rating list, until they have completed events with a total of at least 30 games;
W Score; 1.0 for a win, 0.5 for a draw
We Expected score based on Ro
| Rating difference | Winning Expectancy |
| 736+ | 100% |
| 735 | 99% |
| 500 | 96% |
| 450 | 94% |
| 400 | 92% |
| 350 | 89% |
| 300 | 85% |
| 250 | 81% |
| 200 | 76% |
| 150 | 70% |
| 100 | 64% |
| 50 | 57% |
| 25 | 53% |
| 0 | 50 |
| -25 | 47% |
| -50 | 43% |
| -100 | 36% |
| -150 | 30% |
| -200 | 24% |
| -250 | 19% |
| -300 | 15% |
| -350 | 11% |
| -400 | 8% |
| -500 | 4% |
| -735 | 1% |
| -736+ | 0% |