The ATP Rankings, as defined by the Association of Tennis Professionals (ATP), are the "objective merit-based method used for determining qualification for entry and seeding in all tournaments for both singles and doubles, except as modified for the ARAG ATP World Tour Team Championship and Barclays ATP World Tour Finals (singles or doubles)."^[1] The rankings period is "the immediate past 52 weeks, except for: Barclays ATP World Tour Finals, singles and doubles, which is dropped on the Monday following the last ATP World Tour event of the following year; Futures Series tournaments that are only entered into the system on the second Monday following the tournament's week. Once entered, all tournaments, except for the Barclays ATP World Tour Finals, remain in the system for 52 consecutive weeks."^[1]

A player's ATP Ranking is based on the total points he accrued in the following 19 tournaments (18 if he did not qualify for the Barclays ATP World Tour Finals):

• The four Grand Slam tournaments
• The eight mandatory ATP World Tour Masters 1000 tournaments,^[2]
• The previous Barclays ATP World Tour Finals count until the Monday following the final regular-season ATP event of the following year.^[3]
• The best six results from all ATP World Tour 500, ATP World Tour 250, ATP Challenger Tour, Futures Series, Olympics and Davis cup tournaments played in the calendar year^[4]

The requirement to play in four ATP World Tour 500 events does not apply to a player who was outside the top 30 in the previous year-end ranking; however, no more than four of his results from 500 level events may be counted.^[1] For a better result within the same tour type to be transposed one has to wait for the expirement of the first worse result from previous year. It only expires at the drop date of that tournament and only if the player reached a worse result or hasn't entered the current year.

The Monte Carlo Rolex Masters 1000 became optional in 2009, but if a player chooses to participate in it, its result are counted and his fourth-best result in an ATP 500 event is ignored (his three best ATP 500 results remain). If a player doesn't play enough ATP 500 events and does not have an ATP 250 or Challenger appearance with a better result, the Davis Cup is counted in the 500's table (if he entered or achieved better results). If a player doesn't play enough ATP 250 or Challenger events, the World Team Championship is counted in the 250's table (if he entered or achieved better results).^[5]

For the Davis Cup points, point are only distributed for the World Group countries and instead of having an exact drop date they are gradually updated at each phase of the cup (compared to the results of the player from previous year and arranged his total sum of Davis Cup points to it. E.g. if a player played two matches in a semifinal but plays one the next year only that one missing match will be extracted from his points)^[5]

A player who is out of competition for 30 or more days, due to a verified injury, will not receive any penalty. The 2010 Barclays ATP World Tour Finals will count as an additional 19th tournament in the ranking of its eight qualifiers at season's end.^[6]

For every Grand Slam tournament or mandatory ATP World Tour Masters 1000 tournament for which a player is not in the main draw, and was not (and, in the case of a Grand Slam tournament, would not have been, had he and all other players entered) a main draw direct acceptance on the original acceptance list, and never became a main draw direct acceptance, the number of his results from all other eligible tournaments in the ranking period that count for his ranking is increased by one.^[1]

Once a player is accepted in the main draw of a Grand Slam or ATP World Tour Masters 1000 tournament,^[7] his result in this tournament counts for his ranking, regardless of whether he participates. A player's withdrawal from an ATP World Tour 500 event, regardless of whether the withdrawal was on time, results in a zero point included as one of his best of four results. Further non-consecutive withdrawals results in a zero point allocation replacing the next best positive result for each additional withdrawal.^[1]

Players with multiple consecutive withdrawals who are out of competition for 30 days or longer because of injury are not subject to a ranking penalty as long as verified and approved medical forms are provided; or, a player will not have the ranking penalty imposed if he completes the Promotional Activities requirement as specified under "Repeal of Withdrawal Fines and/or Penalties" or if the on-site withdrawal procedures apply. Players may also appeal withdrawal penalties to a Tribunal who will determine whether the penalties are affirmed or set aside.^[1]

Points distribution as of 2009

• (ATP 1000 series) Qualifying points changes to 12 points only if the main draw is larger than 56
• (ATP 500 series) Qualifying points changes to 10 points only if the main draw is larger than 32
• (ATP 250 series) Qualifying points changes to 5 points only if the main draw is larger than 32

In addition qualifiers and main draw entry players will then also receive the points in brackets for the rounds they reached.^[8]

Points distribution in 2008

Current rankings

Number one ranked players

The following is a list of players who have achieved the number one position in singles since the inception of the rankings in 1973: