The game of soccer is governed primarily by rules from the Federacion Internationale de Football Association, or FIFA. One of those areas governed by FIFA is the quality of the ball used in competition. Air pressure of the soccer ball is one of those topics covered in the laws of the game.
FIFA laws state the air pressure in a regulation ball must be between 8.5 psi and 15.6 psi. Before every game, referees check the ball to make sure it is suitable for play.
Effects of Air Pressure
When a soccer ball is inflated with less than 8.5 psi, it is more difficult to kick and send down the field and is considered too flat. Too much air pressure and the ball is harder to control -- it bounces a bit more and is harder. This is particularly evident when you receive a pass from a teammate, as the ball typically bounces off the foot further than with a properly inflated ball.
Purchased soccer balls come with recommendations for air pressure particular to the ball. Most sporting goods stores also sell air pressure gauges that you can use to check the air pressure in the ball, as well as hand pumps for inflation. Check the ball before play for rips or tears which could affect inflation. Even the newest soccer ball will lose some air pressure after a while.
In youth soccer leagues, the size of the ball is a little smaller than the regulation soccer ball, to account for smaller players. Although a FIFA-regulated ball is usually 26 to 27 inches in diameter, a youth ball is typically 23 to 24 inches in diameter for players under 8 years old, according to the US Youth Soccer Association. Some retailers have also made buying soccer balls easier by listing a number code next to the size of the ball. The smallest youth soccer ball is a 3. The next size up is a 4, then 5 for adults and teens.