Basketball PSI: How Much Air an NBA Basketball Needs, per the Rulebook

Rule 1, Section II of the NBA playing rules covers equipment, and item f(1) says the ball shall be an officially approved NBA ball between 7½ and 8½ pounds pressure. The same range appears a second time in Rule 2, which describes the duties of the officials. Section II, item f of that rule says the officials must check the game balls to see that they are properly inflated, and that the recommended ball pressure should be between 7½ and 8½ pounds.

The rulebook writes the unit as "pounds pressure". It does not write psi or say per square inch. Ball pumps and the NBA's own overview page, quoted below, use pounds per square inch, and this page reads the rulebook figure in those units. On that reading, a pump gauge showing 8.0 is in the middle of the rulebook range. Put plainly, the psi for basketball games in the NBA is 7.5 to 8.5, so the basketball pressure psi for an NBA game is 7.5 to 8.5, and a ball with less air or more air than that is outside the basketball psi the rulebook allows. Basketball pressure psi is measured with a needle gauge, and the air in the ball is what the officials check.

The conversions in the table are calculated from the rulebook figures: one pound per square inch is 6.8948 kilopascals, or 0.068948 bar. The rulebook itself gives only the pounds figure.

The NBA's overview page, the page called About the NBA, describes the ball in one sentence: it says the basketball measures 9 inches in diameter and must be inflated to between 8.5 and 9.5 pounds per square inch. That range is one pound higher than the rulebook range at both ends, and the two ranges overlap at only one value, 8.5.

The page cannot tell which of the two is the intended figure, and neither can the rulebook, which does not mention the overview page. What can be said is which document the people on the court use. The officials work from the playing rules, and Rule 2 requires them to inspect and approve all equipment, including the balls, before the game starts, and to check that the balls are properly inflated. For that reason this page follows the rulebook range, 7½ to 8½ pounds, and shows the other range as a different statement from the same league.

Anyone setting up a ball for a game played under NBA rules should use the rulebook range. A reading of exactly 8.5 satisfies both statements, which makes it the one value that is safe under either source.

Apart from the pressure range, the NBA rulebook says very little about the ball itself. It does not give a circumference or a weight in Rule 1 or Rule 2; it requires an officially approved NBA ball. The size and weight of a men's professional ball come from the manufacturer. Wilson, which makes the NBA Official Game Basketball, says in its guide to choosing a basketball that a size 7 ball measures 29.5 inches around and weighs 22 ounces, and that size 7 is the standard for men's professional leagues.

Rule 1 also says a minimum of nine balls must be made available to each team for pre-game warmup. Rule 2 adds that the officials inspect and approve all equipment before the game, and that all equipment used must be appropriate for basketball. The rulebook also forbids the use of any foreign substance during games, defined as any substance that is applied to a player's body, uniform or equipment, or to any game equipment, with the intention of providing a competitive advantage.

The NBA rulebook states the pressure in pounds, which is shorthand for pounds per square inch. In kilopascals, the unit most of the world uses, one psi is 6.894757, and in bar one psi is 0.0689476. The ranges convert as follows.

The conversions are calculated from the figures in the rulebooks and rounded. They show how much firmer a football is than a basketball: the NFL range sits about five pounds above the NBA range, which is roughly two-thirds more pressure at the lower limits.

Both rulebooks say what happens when a ball is wrong. In the NFL, if a team's ball does not conform to the specifications, or its supply is exhausted, the Referee secures a proper ball from the opposing team and, failing that, uses the best available ball, and the circumstances must be reported to the Commissioner. In rain or on a wet, muddy or slippery field a playable ball is used at the request of the offensive team's center, and the game clock does not stop for it unless undue delay occurs.

Rule 2 adds that all equipment used must be appropriate for basketball. The rulebook gives a range and not a single target, so a ball is within the rule at any pressure between the two limits. The NBA rule is the check before the game: the officials must check that the game balls are properly inflated, the home team must have the minimum of nine balls available to each team for warm-up, and any equipment that is unnatural and designed to gain an advantage may not be used.

Pressure is the figure people look for in a basketball because the ball is inflated and its feel depends on it. The two other American balls are specified differently, and the comparison helps with the units. Pressure here is measured in pounds per square inch, or psi, and one psi is 6.894757 kilopascals, so the NBA range of 7½ to 8½ pounds of pressure is about 51.7 to 58.6 kilopascals.

The NFL rulebook says the ball is made up of an inflated urethane bladder, 12½ to 13½ pounds, enclosed in a leather case, and that the Referee is the sole judge of whether every ball offered for play meets the specification. A League-approved inflation measurement device is provided to the officials for every game, and the home club furnishes a pump. Each team makes 12 primary balls, 12 backup balls and three specially marked kicking balls available for testing no later than two hours and 15 minutes before the game. The Official Baseball Rules specify the baseball by materials and measures only: a ball covered in white horsehide or cowhide, five to 5¼ ounces and nine to 9¼ inches in circumference, with no air in it.

In basketball the officials check that the game balls are properly inflated, and the recommended pressure is between 7½ and 8½ pounds. The rules treat inflation as something the officials check and the teams supply, in the same way as the football rulebook does with a different range.

The pressure range comes from the official 2025-26 NBA playing rules, Rule 1, Section II, item f(1) and Rule 2, Section II, item f. The other range comes from the About the NBA page.

The ball size and weight come from Wilson's guide to choosing a basketball, which is the manufacturer's statement and not part of the rulebook.

This page covers the NBA only. Other organisations that publish their own rules for the ball are not part of it. The figures are current as of October 2026 and will be checked again when a new rulebook edition is published. More basketball pages are collected on the NBA hub, and the page on the height of NBA rims covers the basket.