To keep it simple, there are four major world rankings in what tennis is concern. One for junior players – the Juniors ITF rankings, two for professional players, the currently called the South African Airways ATP Rankings for men and the WTA Rankings for women and the fourth one for senior players – the Senior ITF Rankings. ITF also computes a wheelchair players ranking.
The Juniors ITF Rankings is, since 2004, a Combined Junior Ranking computed by the International Tennis Federation. Combined because contrary to the ATP World Ranking both single and doubles match add up to a players ranking. According to the ITF the “ introduction of the Combined Junior Ranking aims to encourage the doubles game at junior level and subsequently at professional level.”
On how does it work the best to do is the quote ITF “Ranking Explained” page:
“A player’s ranking is calculated using the best six singles results plus one quarter (25%) of the best six doubles results. For example:
Best 6 Singles results = 950
Best 6 Doubles results = 880
One quarter of 880 = 220
950 + 220 = 1170 = Combined Ranking points total
Points continue to be counted on a 52 week rollover system.”
For the ITF Juniors Ranking count several tournaments with different weights from Grand Slams (the same as for professional tennis players) to the grade A events and cups and opens worldwide.