Editing Elo rating system (section)

=== United States Chess Federation ratings ===
The [[United States Chess Federation]] (USCF) uses its own classification of players:<ref>[http://archive.uschess.org/ratings/ratedist.php US Chess Federation] {{webarchive|url=https://web.archive.org/web/20120618103954/http://archive.uschess.org/ratings/ratedist.php |date=2012-06-18 }}</ref>
*2400 and above: Senior Master
*2200–2399: National Master
**2200–2399 plus 300 games above 2200: Original <!--The title has been changed, though I am too lazy to find a source--> Life Master<ref>[http://main.uschess.org/content/view/7327#Master USCF Glossary Quote:"a player who competes in over 300 games with a rating over 2200"] {{Webarchive|url=https://web.archive.org/web/20130308182917/http://main.uschess.org/content/view/7327#Master |date=2013-03-08 }} from The United States Chess Federation</ref>
*2000–2199: Expert or Candidate Master
*1800–1999: Class A
*1600–1799: Class B
*1400–1599: Class C
*1200–1399: Class D
*1000–1199: Class E
*800–999: Class F
*600–799: Class G
*400–599: Class H
*200–399: Class I
*100–199: Class J

====The K-factor used by the USCF====
The ''K-factor'', in the USCF rating system, can be estimated by dividing 800 by the effective number of games a player's rating is based on ({{math|''N''<sub>''e''</sub>}}) plus the number of games the player completed in a tournament ({{mvar|m}}).<ref>[http://www.glicko.net/ratings/approx.pdf "Approximating Formulas for the US Chess Rating System"] {{Webarchive|url=https://web.archive.org/web/20191104083935/http://www.glicko.net/ratings/approx.pdf |date=2019-11-04 }}, [[United States Chess Federation]], Mark Glickman, April 2017</ref>
: <math>K = \frac{800}{N_e + m} \, </math>

====Rating floors====
The USCF maintains an absolute rating floor of 100 for all ratings. Thus, no member can have a rating below 100, no matter their performance at USCF-sanctioned events. However, players can have higher individual absolute rating floors, calculated using the following formula:
:<math>AF = \operatorname{min}\{100+4N_W+2N_D+N_R , 150\}</math>

where <math>N_W</math> is the number of rated games won, <math>N_D</math> is the number of rated games drawn, and <math>N_R</math> is the number of events in which the player completed three or more rated games.

Higher rating floors exist for experienced players who have achieved significant ratings. Such higher rating floors exist, starting at ratings of 1200 in 100-point increments up to 2100 (1200, 1300, 1400, ..., 2100). A rating floor is calculated by taking the player's peak established rating, subtracting 200 points, and then rounding down to the nearest rating floor. For example, a player who has reached a peak rating of 1464 would have a rating floor of {{math|1=1464 − 200 = 1264}}, which would be rounded down to 1200. Under this scheme, only Class C players and above are capable of having a higher rating floor than their absolute player rating. All other players would have a floor of at most 150.

There are two ways to achieve higher rating floors other than under the standard scheme presented above. If a player has achieved the rating of Original Life Master, their rating floor is set at 2200. The achievement of this title is unique in that no other recognized USCF title will result in a new floor. For players with ratings below 2000, winning a cash prize of $2,000 or more raises that player's rating floor to the closest 100-point level that would have disqualified the player for participation in the tournament. For example, if a player won $4,000 in a 1750-and-under tournament, they would now have a rating floor of 1800.