How ratings work

Every player on The Hill has a rating worked out from every rack of every match on record: 12,295 matches between 1,454 players so far. Higher is better, and the gap between two ratings says how a match between them should go.

The scale

A 100-point edge means 2-to-1 odds on each rack: a player rated 600 wins about two racks in three against a player rated 500, and about four in five against one rated 400. It's the same odds scale FargoRate uses, so the numbers feel familiar, but these ratings are The Hill's own, worked out from the matches here.

How it's worked out

Ratings come from a Whole-History Rating (Rémi Coulom, 2008), fitted to racks rather than wins and losses, so a 7–6 match says less than a 7–1. Every player has a rating on every day they played, and all of them are fitted together: beating someone counts for more when that someone has beaten strong players. A player's skill is allowed to change over time, by about 40 points a year on average, so recent results count for more than old ones without old ones being thrown away.

• A new player starts at 500 with a wide margin (±200), which their first results quickly move.
• A rating is provisional until it rests on 50 racks.
• Each game (9-Ball, 10-Ball, 8-Ball, One Pocket, Back Pocket 9-Ball, Snooker, Three-Cushion, Chinese 8-Ball) has its own rating. A player's rating in one game starts from their ratings in the others and usually stays within about 100 points of them, so a 9-ball player who takes up one pocket doesn't start from scratch.
• All ratings are refitted from the whole history every night, and the players in a new match are updated straight away.

What counts

• Confirmed results. A score a player enters counts once it's backed: by the opponent confirming it, by witnesses, or by the record of whoever entered it. A disputed score doesn't count. Results from leagues and tournament brackets count as confirmed.
• Singles matches. Scotch doubles and three-player games are kept on the record but don't move ratings, and nor do handicapped matches (a spot) or practice.

Where results come from

Players enter matches or score them live at the table in the app. League results come in from CompuSport, and tournament brackets from DigitalPool, Challonge, CloudSnooker and CompuSport, as the events are played. Every result has its own page, so a rating can always be traced back to the matches behind it.