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How a rating ladder works in a club

A rating ladder gives every player a number that goes up after a win and down after a loss. It helps you make even games, and it lets players follow their own progress. Players only trust it if they know what moves the number, so this guide says exactly what ShuttlePilot does.

The idea

ShuttlePilot uses an ELO rating, the system first made for chess. Before a match, the ratings of the two sides give an expected result. After the match, the ratings move by how far the result was from that expectation. In doubles, a side's rating is the average of the two partners. What the winners gain, the losers lose.

What moves a rating

Only a saved result. Three things decide how much it moves:

1. Who won.
2. How strong the two sides were. Beating a stronger side gains more than beating a weaker one, and losing to a weaker side costs more. A side 200 points above its opponents is expected to win about three matches in four.
3. The margin in points. The app adds up the points of all sets and looks at the difference. A close match moves ratings a little and a one-sided match much more: a 21-0 moves them about five times as much as a 21-19. Because the margin is counted in points, short sets move ratings less: an 11-0 counts the same as a 21-10.

In doubles, the two partners share the side's change. If it is an odd number, one of them gets the extra point. In singles, the player gets all of it.

Some numbers

For a doubles match, with the standard settings:

Why a close loss to stronger players costs little

Two reasons add up. The weaker side was expected to lose, so the loss tells the ladder little. And the margin was small, so the change is small too. Losing 19-21 to a side 200 points stronger costs the side one point in total. That is on purpose: nobody should avoid strong opponents to protect their number.

Where a new player starts

At 1500, unless the trainer gives a different starting rating when adding the player. Until results come in, the app cannot know who is stronger, so the first evenings are less even than later ones.

A club that has kept its results in a spreadsheet can import them, and the ladder is worked out from those matches. Do it before the first night, because an import later works out the whole ladder again. Changing a player's starting rating later works out the ratings again from the first match, but only when a club admin makes the change, after a confirmation. If another trainer makes it, the rating is saved and the ladder stays as it is.

Good to know

• A rating changes the moment a result is saved, and the next round is built on the new ratings. If a result is corrected or deleted, the app works out every later change again, as if the right result had been entered from the start.
• A result where both sides won the same number of sets and the same number of points has no winner and changes no ratings.
• On a rotation court, you record who came out on top, not a score. Between even players, the winner of a three-player rotation gets +2, and the other two get −1 each.
• Players who sit out keep their rating.
• A club admin can hide ratings from players. Trainers still see them, and the rounds are still balanced on them.
• The ladder is your club's own. It has nothing to do with any national ranking list.