I guess that you want to say 'Elo difference into expected score'. The classical, well-known Elo formula is:Henk wrote:Someone told me that the chance of a draw from 2200 against 2600 player would be higher than a draw from 1800 against 2200 player. So that is nonsense.

By the way how do you convert ELO rating back into chance.

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```
(Elo difference) = (own rating) - (opponent's rating)
(Expected score) = 1/{1 + 10^[-(Elo difference)/400]} = (win ratio) + 0.5*(draw ratio)
(Win ratio) + (draw ratio) + (lose ratio) = 1
It is useful with thousands of games. You can not claim anything with 10 games or so.
There are error bars that are proportional to (games)^(-0.5).
There is much information about error bars in this forum.
```

Kai stated a 700-Elo difference and a 3% of draws IIRC. Just using the Elo formula:

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```
1/{1 + 10^[-(700)/400]} ~ 0.9825 = 98.25% (for the stronger engine).
1/{1 + 10^[-(-700)/400]} ~ 0.0175 = 1.75% (for the weaker engine).
If the weaker engine can not win a single game after lots of games (win ratio = 0):
(Draw ratio) = [(expected score) - (win ratio)]/0.5 = (0.0175 - 0)/0.5 = 0.035 = 3.5%
```

Draw Rate

I hope this info could be useful to you.

Regards from Spain.

Ajedrecista.