A hard court is not one surface. The International Tennis Federation, which writes the technical standards for the sport, puts every court on a single scale called the Court Pace Rating, and sorts surfaces into five categories from slow to fast according to where they land. The number decides which ball a tournament should use, and in the ITF’s own team competitions it sets a hard limit on how quick or slow a home nation may make its court. With the season now on the hard courts of the Asian swing and heading indoors for Europe, it is the governing body’s measure of what players mean when they call a court quick or slow.
Everything below comes from the ITF’s 2026 technical booklet, ITF Approved Tennis Balls, Classified Surfaces and Recognised Courts, which is effective from 1 January to 31 December 2026, and from the 2026 Billie Jean King Cup Regulations.
What the number measures
Court Pace Rating, or CPR, measures what happens to the ball when it hits the court. Two properties matter. The first is friction: a rougher surface grips the ball harder and takes more speed off it horizontally, so it plays slower. The second is restitution, the energy the surface gives back upwards. A surface that sends the ball up higher is also perceived to play slower, the ITF explains, because the player has more time to reach it.
CPR combines the two in one formula: 100 multiplied by one minus the coefficient of friction, plus 150 multiplied by the difference between 0.81 and the coefficient of restitution. The 0.81 is the ITF’s mean restitution value across all surface types, and the restitution figure is corrected for the temperature of the test balls. A court scores higher, and so counts as faster, when friction goes down, when the bounce goes down, or both.
How the test is done
The ITF test method, coded ITF CS 01/02, uses a compressed-air ball cannon. It fires a ball at the court at 30 metres per second, plus or minus two, at an angle of 16 degrees, with almost no spin: no more than three revolutions per second. Instruments measure the ball’s horizontal and vertical speed before and after the bounce to within 0.05 metres per second, and friction and restitution are calculated from those readings.
Three high-specification test balls are fired three times each, for nine impacts, with the impact point moved every time. On site, the ITF recommends testing in at least four locations covering heavily and lightly used areas of the court, and the result is the mean rating for all impacts excluding the lines. Grass and artificial grass, which have a grain, are tested in the direction of play. Testing should not go ahead if the average temperature of the balls cannot be kept between 10 and 30 degrees Celsius. In the laboratory, samples at least half a metre square are conditioned at 23 degrees for three hours first.
The five categories
- Category 1, slow: a CPR of 29 or lower. Most clay courts and other unbound mineral surfaces fall here.
- Category 2, medium-slow: 30 to 34.
- Category 3, medium: 35 to 39. The ITF says most acrylic-coated surfaces and some carpets fall in categories 2 and 3.
- Category 4, medium-fast: 40 to 44.
- Category 5, fast: 45 or higher. Most natural grass, artificial grass and some carpets fall in categories 4 and 5, according to the ITF.
The categories describe pace only. The ITF is explicit that classification is not an approval or endorsement of a product, and that a product can be refused classification if the ITF considers it unsuitable for tennis.
How precise it is
The rating is not exact, and the ITF says so. Round-robin testing between accredited laboratories puts the uncertainty of the method at plus or minus two points. When a surface’s mean rating is within two points of the next category, the manufacturer is allowed to choose which of the two categories it is listed in.
Installation adds more variation. For a new court built by experienced contractors with quality materials, the ITF’s guide tolerance is five points either side of the product’s quoted rating, and the difference between test locations on the same court should not exceed ten points. The layers underneath the playing surface can change the reading too. ITF classification of a surface product lasts three years, after which it must be retested to stay on the list.
Which ball goes with which court
The reason the ITF classifies courts at all is to match them to balls. The Rules of Tennis approve three standard ball types. Type 1, the fast ball, is intended for slow courts. Type 2, the medium ball, is intended for medium-slow, medium and medium-fast courts. Type 3, the slow ball, is intended for fast courts; it is physically larger, between 7.00 and 7.30 centimetres across against 6.54 to 6.86 for the other two, and the ITF also recommends it for play at altitudes above 1,219 metres on any surface. The ball, not only the court, therefore shapes how quickly a match plays. For more on the balls the majors use, see our guide to tennis balls at the major tournaments.
Where the rating becomes a rule
For most tournaments the ITF’s test methods are recommendations, not requirements; the booklet says so in capital letters. The ITF’s team competitions are different. Under the 2026 Billie Jean King Cup Regulations, any court other than grass or clay used in the competition must have a measured Court Pace Rating between 24 and 50 inclusive, tested with the ball chosen for the tie. Hard courts at the Finals, the Qualifiers and the Play-offs must be ITF-classified surface products.
That matters because the home nation in a Qualifier or Play-off tie chooses the surface and the ball, and a very fast or very slow court is an obvious way to tilt a tie. If on-site testing shows the match court is outside the permitted range, the ITF’s Internal Adjudication Panel can dock Nations Ranking points, impose a fine, withhold payments, strip the nation of its future choice of ground, relegate it, disqualify it or order it to compensate the visitors. We explain the competition’s structure in How Billie Jean King Cup Works and its men’s counterpart in How Davis Cup Works.
What the number does not tell you
A Court Pace Rating describes one court on one day. The ITF notes that a surface’s properties change with the weather, with use and with maintenance, and its court recognition scheme states that test results are valid only for the day they were taken. An acrylic court needs about a week to settle after it is laid before it is tested, and clay or artificial grass can take months.
The rating also measures only the ball and the surface. It says nothing about air density, altitude or humidity, and the ITF’s own tolerances allow two new courts laid with the same product to test several points apart. That wider picture is covered in our explainers on why hard courts do not all play the same and why court surfaces matter.
