Foldit ranks players and groups according to the "global points" they've received on completed puzzles.
The basics of the ranking system are as follows:
- Separate rankings are maintained for soloists, evolvers, and groups.
- Each puzzle is assigned a number of "global points", normally 100.
- The top soloist, evolver, and group receive the assigned number of global points at the end of each puzzle.
- Other players and groups receive a smaller number of points based on the number of participants.
- The main soloist, evolver, and group rankings are determined by adding the global points received in the last 120 days. ("Beginner" puzzles are not counted for the group ranking, however.)
- Weekly and monthly rankings are also available. These use cutoffs of 7 and 30 days, respectively.
- The soloist hall of fame ranks players by the total global points received as a soloist, regardless of when the points were earned.
- Each puzzle is assigned to one or more categories, such as "beginner", "prediction", and "design". Players and groups are ranked within each category based on rule specific to the category.
- Players and groups must keep playing to maintain their rank.
"Global Points" formula
The formula for assigning "global points" is found in the technical questions section of the Foldit FAQ, and is expanded here.
The formula uses three variables to calculate the global points assigned for a given puzzle::
X: Points the puzzle is worth (shown on puzzle page, typically 100) R: Final rank when the puzzle closed, minus 1 (for example, rank 20 gives R = 19) N: Number of competitors minus 1 (for example, 275 competitors gives N = 274)
The number of soloist players in the puzzle is used for both soloist and evolver scores. The number of teams competing in the puzzle is used for group scores. The number of competitors can be found by checking the puzzle page after the puzzle closes.
In Excel spreadsheet syntax, the formula is:
Points = Max ( 1, RoundUp ( ( ( 1 - R / N ) ^ 5 ) * X ) )
In Open Office spreadsheet syntax, the formula is:
Points = Max ( 1; RoundUp ( ( ( 1 - R / N ) ^ 5 ) * X ) )
In Lua, the formula is:
Points = math.max ( 1, math.ceil ( ( ( 1 - R / N ) ^ 5 ) * X ) )
The "max" function in the formula formula assures that at least one point is assigned.
Smaller values of "N" mean the number of points assigned per rank drops off sharply. The number of soloists, typically 200 or more, is used to assign both soloist and evolver points. The number of groups, usually less than 50, is used to assign group points. As a result, the difference in the points awarded for first and second place is much more pronounced in the group competition.
Procedure for determining the number of competitors
The Foldit web site does not directly show the number of competitors. To see the number of competitors after a puzzle has closed, go the puzzle's page.
For soloist and evolver competition, go to the "Top Soloists" section and click "show all' at the end of the list. On the resulting page, click "last". The rank of the last player listed is the number of competitors.
For group competition, go the "Top Groups" section of the puzzle page, then click "show all", followed by "last" on the resulting page. The rank of the last group listed is the number of competitors for the evolver competition.
Other types of rankings
In addition to the main 120-day ranking for soloists, evolvers, and groups, Foldit maintains several other types of rankings. These rankings are also based on the "global points" formula described above, but the totals are tabulated differently.
Soloist hall of fame
The http://fold.it/portal/players/s_ever soloist hall of fame] shows the total number of points received by each soloist player. These points never expire. There is no evolver or group hall of fame.
Weekly and monthly rankings
Foldit also maintains rankings of players by week (7 days) and month (30 days). These rankings are similar to the main 120-day ranking, in that they use a date-based cutoff. These rankings include:
Groups are ranked weekly or monthly.
Foldit assigns each puzzle to one or more categories, such as "overall", "prediction", "design", and "symmetry". Foldit maintains separate rankings by category. Unlike date-based rankings, category rankings use a "your best x out of the last y puzzles" tabulation. For example, the "overall" category uses the a contestant's best 40 out of the last 50 puzzles in the category, while the "prediction" category uses the best 8 out of 10 puzzles.
The puzzles that count toward the category ranking at a point in time are shown on the category page. The list of puzzles is the same for all players and groups. The list does not depend of which puzzles a contestant has played.
To see the complete list of puzzles, visit the category's detail page, for example "prediction". Under "Puzzles" there's a list of "Closed" puzzles. Click "show all" to see the complete list, for example closed prediction puzzles. Puzzles which are no longer counted toward the category ranking are available by the "show old puzzles" link.
Category rankings are shown on the category pages and also on each player and group page.
The technical questions section of the Foldit FAQ documents the formula for assigning global points.
The Global Points calculator spreadsheet on the German Foldit wiki.
Feedback 989490 - "4 month scoring window - how is it calculated? v3" documents the 120, 30, and 7 day cutoffs used in tabulating rankings.