How ATP and WTA rankings work
The 52-week rolling system explained: mandatory events, points defence, qualifying cut-offs and what really moves the rankings.
The 52-week rolling system
Both the ATP and WTA rankings are not season-by-season. They are a rolling 52-week window: every Monday a new ranking is published using the points each player has scored over the previous 52 weeks. Last year's Australian Open is replaced this week by this year's Australian Open — that is why January and the European clay swing are points-defence minefields.
Mandatory and best-of counting events
For the men, the ATP counts 19 results: the four Grand Slams, the eight Masters 1000s, plus the seven best other results from ATP 500s and 250s. The Tour Finals add a further set on top. For the women, the WTA counts 16 results — the Slams, the four WTA 1000 mandatory events, the best two of the partial 1000s, and the best six of everything else, plus the WTA Finals.
Points defence
A player who won a tournament a year ago will lose every point from that title the day the new edition begins, replaced by whatever they earn this year. Defending a Grand Slam title means defending 2,000 points; failing to reach the second week typically means a heavy ranking drop.
Why the World No. 1 changes
World No. 1 changes hands when the chasing player's points-gained at an event exceeds the leader's points-defended. That is why a Masters 1000 final in March can flip the rankings even though the leader did not lose.