The three major tennis ratings are
NTRP - The oldest tennis ratings system was mainly designed for the USTA Adult League program for players at least 18 years of age.
From the USTA website:
An NTRP Rating is a numerical indicator of tennis-playing ability, from 1.5 (beginner) through 7.0 (touring pro), which aligns with a set of general characteristics that break down the skills and abilities of each level, in 0.5 increments. Ratings are generated by play in USTA Adult Divisions of 18 & Over, 40 & Over, 55 & Over, 65 & Over, Mixed 18 & Over, Mixed 40 & Over and Mixed 55 & Over. In some sections, results from USTA Sanctioned Tournaments and additional leagues may be included in the Rating calculation. Ratings help establish a player’s NTRP skill level after only a few matches and do not change dramatically. Rather, they slowly increase or decrease over time as they reflect consistent player skill levels as exhibited through play results.
For example, a player with a 1.5 NTRP rating who has had limited experience with stroke development is still working primarily on getting the ball into play and is not yet ready to compete. By contrast, a 3.0 player is fairly consistent when hitting medium-paced shots but is not comfortable with all strokes and lacks execution when trying for directional control, depth, pace, or altering the distance of shots.
At the top of the rating spectrum, a 6.0 player typically has had intensive training. They have likely played international tournaments or top-level collegiate competitions and have obtained a national ranking. The 6.5 and 7.0 are world-class players.
To find NTRP Rating information click here"
UTR - Universal Tennis (UTR) is a global rating system that promotes fair and competitive play across the tennis world. All players, regardless of age, gender, geography or skill level, are rated on a same scale between 1 and 16.50 based on actual match results.
From the Tennis CT website: UTR provides a real-time view of a player’s true skill level. Having a UTR enables you to track your progress, find level-based play, and expand your tennis network to play with people across age, gender and tennis silo. Every tennis player can have a UTR. UTR provides an accurate measurement of a player’s true skill level, whether you are a recreational, junior, high school, college or pro player. UTR is calculated by an algorithm using a player’s last 30 eligible match scores from the last 12 months. For each eligible match, the algorithm calculates a match rating and a match weight; a player’s UTR is the weighted average of all the match ratings.
WTN - World Tennis Number is the latest and newest rating system commissioned by the ITF (International Tennis Federation).
From the ITF website: The ITF World Tennis Number is a new rating system for all tennis players across the world which will make it easier for everyone who plays tennis in Britain to organise and play against opponents of a similar standard.
From the UK's LTA website:
The ITF World Tennis Number has…
A world-wide rating system that ranges from 40 (recreational players) to 1 (pro players) - players with an ATP/WTA ranking will be listed as PRO
Separate ratings for singles and doubles players
An algorithm that produces your own rating
An algorithm that counts sets, and matches, played which means the more you compete, the more accurate your rating will be
A personalised digital ‘Game zONe’ feature, which will help you identify opponents with a similar rating online
The following is a conversion chart that ties the three ratings system together. Since UTR distinguishes between male and female ratings, we have included a chart for each gender.