How this calculator works
The ITF rules of tennis set the ball change: new balls start the match, they are changed after the first seven games, and thereafter after every nine games. A match that ends before the first change uses one set of balls. Longer matches add a set for each block of nine games after the first change. This page applies that rule to the average games per match, multiplies by the number of matches, and adds an allowance for balls lost to the crowd. The mass estimate uses the ITF minimum and maximum ball mass, with 58 grams as a working value.
Formula
Sets of balls = 1 if games are 7 or fewer, otherwise 2 + floor((games - 8) / 9). Balls per match = sets x balls per change. Total balls = matches x balls per match x (1 + loss rate), rounded up. Mass = total balls x 58 g.
Worked example
At 22 games per match, the first change comes after game 7 and the second after game 16, so the match uses 3 sets of 6 balls, or 18 balls. One hundred matches need 1,800 balls before losses; a 5 percent loss allowance raises that to 1,890 balls, with a mass of about 110 kg.
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Frequently asked questions
Why six balls at a time?
Six balls let players serve with a choice of balls and keep the pace moving. The exact number is set by the tournament and the rules of the event, so enter the value your event uses.
When are balls changed?
The standard professional rule is after the first seven games and then every nine games. A tie-break counts as one game for the change. Some events use different rules, especially in doubles or at junior level.
How much of a tennis ball is rubber?
A ball is a hollow rubber core covered in felt. The mass here is the whole ball, not the rubber alone. A used ball can be recycled or repressurised, so the mass is not the same as waste sent to landfill.