Tennis Court Surfaces Explained: Clay, Grass, Hard Courts and the ITF Court Pace Rating

Tennis is played on three main surfaces, clay, hard courts and grass, and the difference between them comes down to what happens in the instant the ball bounces. Clay grabs the ball, slows it and throws it up high, so the receiver has more time. Grass lets it skid through fast and low. Acrylic hard courts sit between the two and can be built faster or slower. The International Tennis Federation (ITF) puts a number on this with its Court Pace Rating, and its rules sort courts into five pace categories, with most clay courts in the slowest and most grass courts in the two fastest.

That one difference changes how often serve is broken, which styles of play are rewarded, and even which ball the tournament has to use. The detail below comes from the ITF Rules of Tennis and the ITF's technical booklet, both in their 2026 editions.

Pace is two numbers, not one

The ITF's technical guide defines the two properties that make a court feel fast or slow.

Friction is the grip between ball and surface, measured as a coefficient of friction (COF). A rougher surface has a higher COF, takes more of the ball's horizontal speed away at the bounce, and plays slower.

Restitution is the energy the bounce gives back, measured as a coefficient of restitution (COR): the ball's vertical speed after the bounce divided by its vertical speed before it. A surface with a higher COR sends the ball up higher. The guide notes this is typically perceived as slower, because the player has more time to reach it.

So "slow" really means two things working together: the ball arrives with less pace, and it sits up longer. A court can be slow mainly through grip, mainly through a high bounce, or both.

How the ITF measures it

The Court Pace Rating test (ITF CS 01/02) works like a controlled serve. A ball projection device, such as a compressed-air cannon, fires a ball at the surface at 30 ± 2 metres per second and an angle of 16 ± 2 degrees, with almost no spin. The ball's horizontal and vertical speeds are tracked before and after the bounce. Three balls are fired three times each, nine impacts in all, at different spots. On grass, natural or artificial, the shots go along the length of the court, the way play runs.

From those speeds the lab calculates the friction and restitution values and combines them:

CPR = 100 × (1 − COF) + 150 × (0.81 − COR)

The COR is corrected to a ball temperature of 23 °C first. The 0.81 is the guide's mean COR across all surface types, and 150 is its "pace perception constant", which sets how much bounce counts compared with friction.

Three courts, worked through

These inputs are illustrative, not measurements of any real court, and assume a 23 °C ball:

Each 0.01 of friction moves the rating by one point, and each 0.01 of bounce moves it by 1.5 points, in the direction intuition gets wrong: a livelier bounce lowers the rating, because it buys the receiver time. The guide's own bands suggest friction usually does more of the sorting: its "medium" COF band runs from 0.56 to 0.70, a spread worth 14 rating points, while its "medium" COR band, 0.79 to 0.84, is worth 7.5.

The guide also gives a tolerance. A new court laid by an experienced contractor should land within ±5 CPR points of the quoted value, and different test spots on the same court should not differ by more than 10 points.

The five categories

The Rules of Tennis turn the rating into five classes and name typical surfaces for them:

Classification is voluntary: any manufacturer, contractor or facility owner may apply. Under the ITF's Court Pace Classification Programme, which replaced an earlier scheme in January 2008, accredited laboratories carry out the testing, and a classification lasts three years. The ITF stresses that a classified product is listed purely on its rating, and that classification is not an endorsement.

Surface by surface

Clay courts are made of crushed shale, stone or brick. The French Open's courts are crushed red brick, often called terre battue, while clay courts in the United States tend to be green clay made of crushed basalt. Clay slows the ball and gives a high bounce, which takes away much of the advantage of a big serve, and the courts need rolling and careful watering.

Hard courts are rigid surfaces such as asphalt or concrete, often covered with an acrylic layer for a consistent bounce. Their speed varies: the amount of sand mixed into the paint changes how much the ball slows. Most sit in the ITF's middle categories.

Grass is grown on very hard-packed soil and is the fastest surface in common use. Bounces are low and depend on how healthy and recently mown the grass is and how worn it has become. Grass is now rare because watering, mowing and drying after rain make it costly.

Carpet means any removable court covering. It is generally fast with a low bounce, and it has disappeared from the top level of the professional game.

At the four majors, the Australian Open and US Open use acrylic-topped hard courts, the French Open is played on clay, and Wimbledon on grass. Wimbledon is the only one never to have changed surface. The Australian Open moved from grass to hard courts in 1988. The US Open has used three: grass until 1974, green clay from 1975 to 1977, and hard courts since 1978.