Wimbledon Keeps Its Tennis Balls at Exactly 20°C to Control Every Bounce

The Science Behind the Bounce

When a tennis ball strikes a court surface and bounces back up, the height of that bounce depends on several factors: the court surface, the angle of impact, the speed of the incoming ball — and the internal air pressure of the ball itself. That last factor is directly controlled by temperature, which is why Wimbledon, the world's most prestigious tennis tournament, maintains its match balls at a precise 20°C (68°F) before they are brought onto the court.

The principle at work is Charles's Law, one of the fundamental relationships in gas physics: at constant volume, the pressure of a gas is directly proportional to its temperature. A tennis ball held at a cold temperature has lower internal air pressure and therefore bounces lower. The same ball at a higher temperature has higher internal pressure and bounces higher. These differences are not enormous, but at the level of professional tennis — where a centimeter of bounce height can determine whether a ball is attackable or not — they matter considerably.

How Wimbledon Controls for This

All Wimbledon balls are stored in temperature-controlled rooms at 20°C and are transferred to the court in insulated containers. The tournament uses the Slazenger Wimbledon tennis ball, which has been the official ball of the Championship since 1902 — the longest continuous sporting equipment sponsorship in history. Each ball is used for approximately seven games before being replaced.

The choice of 20°C is not arbitrary. It represents the approximate ambient temperature of a typical Wimbledon summer day, meaning that balls stored at this temperature should behave consistently whether they are used in morning practice or during an afternoon match in direct sunlight. In practice, balls do warm slightly during play — a ball struck hard by a professional player generates friction heat — but the pre-game temperature control ensures that all balls begin from the same baseline.

Why Consistency Matters at the Highest Level

In recreational tennis, a slightly bouncier or flatter ball is an inconvenience. At Wimbledon, where millimeter differences in shot placement and millisecond differences in reaction time determine outcomes, any variation in ball behavior introduces an element of inconsistency that neither the players nor the tournament organizers want. The temperature control is one of dozens of precision measures Wimbledon employs to ensure that when a player wins, it is because of skill rather than equipment variability.

The grass courts at Wimbledon are cut to exactly 8mm. The balls are pre-warmed to 20°C. The net height is checked before every match. The protocols read less like a sporting event and more like a scientific experiment — which, in a sense, is what elite sports competition aspires to be. Every variable that can be controlled should be controlled, so that the uncontrolled variable — the ability and judgment of the athletes — is what decides the result.

The 20°C tennis ball is a small detail with a large purpose: it is the tournament's commitment to fairness expressed in units of temperature.