Playing conditions
The higher a tournament is played, the thinner the air and the faster the ball. Here is how much that changes the tennis, where it matters on tour, and why DeepCourt marks altitude from 550 m.
Air gets about 1% thinner for every 100 m you climb. A tennis ball is slowed down by the air it pushes through, so in thinner air it keeps more of its speed all the way to the other side of the net.
Spin works through the air too. Topspin brings the ball down because of the way it pushes air around it, so at altitude the same swing dips less and the ball carries further. Serves come through quicker and points get shorter.
Worked out from the international standard atmosphere. On the day, the weather moves it a little either way.
Every outdoor ATP clay match with serve statistics since 2019, grouped by how high the venue is. The higher the tournament, the more points the server wins and the more often serve is held.
| Venue height | Service games held | Serve points won | Aces per 100 serve points | Matches |
|---|---|---|---|---|
| Under 200 m | 75.3% | 60.8% | 4.8 | 6,329 |
| 200–549 m | 77.0% | 61.6% | 5.1 | 1,040 |
| 550–999 m | 80.0% | 63.0% | 6.1 | 1,392 |
| 1,000 m and up | 82.1% | 64.5% | 6.8 | 272 |
Raw figures, not adjusted for which players took part. DeepCourt’s court speed reading does adjust for the players.
The ITF’s Rules of Tennis allow special high-altitude balls above 1,219 m (4,000 feet): pressureless balls, or pressurised balls with a lower internal pressure, made to play more like a standard ball does at sea level. Below that line, tournaments use standard balls.
ITF Rules of Tennis, Appendix IThe effect starts well below the ITF’s line. In the table above, venues under 550 m play almost like sea level, and from 550 m serve is held clearly more often. Players already talk about the ball flying at the Madrid Open, at about 560 m. So on DeepCourt, a tournament gets an altitude mark from 550 m.
Altitude is one of the things DeepCourt’s court speed reading picks up: it measures how fast each tournament actually plays, conditions included.
How court speed is worked outVenue heights from DeepCourt’s venue records, 2026 calendar.