Rating System

How much lower than mine does my opponent’s rating need to be for it to be a +7 win or -9 draw? How much for +6 and -10?

i think i remeber seeing the formula for ratings on wikipedia somwhere

https://support.chess.com/customer/en/portal/articles/1444777-how-do-ratings-work-

It depends on a number of factors. That article is a little old, mainly on the starting rating part, and there is a link at the end to an article that goes into a lot more detail.

I'm talking about like if both players have played like 100 games in the past week. Their ratings are accurate. But if one of them is 1300 and the other is 1375, how much would the 1300 lose if he was beaten?

It still depends, on the RD each player has. But you can see the actual formula here: https://en.wikipedia.org/wiki/Glicko_rating_system

I don't understand any of that. Isn't there a simpler way to put it?

I'm sure there may be some approximation formulas but it's statistics, it's complicated

I found one online calculator (though I'm not sure how they are implementing the RD or how accurate it is) but assuming the RDs were essentially the same, the lower rated player would lose around 30 points (38.8 on that calculator but the USCF one, which uses a formula from the same creator put it closer to 30).

edit: it appears the calculator I was using might not be the best or I need to figure out how they do the RD values

It's pretty easy actually. First of all a win vs an equally rated opponent will get you about 10 points. Chess.com uses Glicko, so it also depends on how new or active your account is (you might gain or lose over 100 points for a single game when you're new) but this is a good estimate.

For more detail:

For wins and draws, find your % below, then multiply by 20. That's your rating change estimate.

For draws subtract or add .5 before multiplying by 20.

(What's going on is this chart gives you the expected score. You subtract this from your actual score. 1 for win, 1/2 for draw, and 0 for loss. Then multiple by the k factor which is usually 20.)

ex.

200 point difference. You're the higher rated player and you win

.24 * 20 = 4.8
So you gain ~4.8 points

150 point difference. You're higher rated and you draw

.5 - .70 = -.2
-.2 x 20 = -4
So you lose 4 points.

That looks like an Elo table to me.

Yeah, it works as an estimate for Glicko

In a perfectly matched game on chess.com, if I win, it's +8, draw, 0 and lose, -8.

And if you just memorize that

0 points is 1/2
100 points is ~ 2/3
200 points is ~3/4
300 points is ~4/5
(which isn't hard, notice the pattern)

Then this method of estimating is really easy to do in your head.

Depends on how active you are in that rating class. It might be 8 for bullet, and 12 for daily (just a random example).

This is what your RD stat is. The higher the RD, the more the change will be.

I'm only talking about when both players have played a BUNCH of recent games recently. I don't care about new accounts or accounts that havent played in a while.

Well "a bunch" isn't a variable in a maths formula, so the best people can give you is an estimate.

The rating change will be about 10, like I told you.

If you play more, then it will be less. Like you said you noticed for you the rating change was 8.

If you play even more frequently, then it will be lower than 8 (but the amount needed to lower the rating change will increase exponentially).

Oh. So if I played like 100 games in one day I would start only winning like 7 per win?

Yeah.

I mean... I don't know how many it would take, but that's the idea, yeah.