How Much Air Should a Soccer Ball Have? PSI by Size and Why Balls Go Flat in Winter

The Laws of the Game put a match ball between 8.5 and 15.6 psi, and that is the only pressure figure in the rulebook — it describes a size 5 ball and nothing else. For a size 3 or size 4 youth ball there is no official number at all, so the range printed on the ball is the one that counts, and it is usually lower. Whatever you set it to in a warm garage, a cold field will quietly take one to three psi back out before kickoff.

Almost every soccer ball pressure chart online gives a confident psi figure for every size. Most of those per-size numbers are invented — no governing body publishes one, which is why the charts disagree with each other and with the label on your child's ball.

Here is what is actually specified, what the printed range is for, and the two things that change the reading between your garage and the first whistle.

How much air should a soccer ball have?

Between 8.5 and 15.6 psi. Law 2 of the IFAB Laws of the Game requires that all balls be:

• spherical
• made of suitable material
• of a circumference of between 68 cm (27 ins) and 70 cm (28 ins)
• between 410 g (14 oz) and 450 g (16 oz) in weight at the start of the match
• of a pressure equal to 0.6–1.1 atmosphere (600–1,100 g/cm²) at sea level (8.5 lbs/sq in–15.6 lbs/sq in)

Read the circumference line and you can see what that pressure range is attached to. A 68–70 cm ball weighing 410–450 g is a size 5. Law 2 describes one ball — the match ball — and the 8.5–15.6 psi window belongs to it.

Size 3 and size 4 balls are not in Law 2 at all. They exist because youth competitions modify the game for younger players, the same way they modify field size and player numbers — our soccer ball size by age guide covers which one your child should be on. The Law has nothing to say about how hard to pump them, and that is the gap every psi chart online fills with a guess.

What psi should each soccer ball size be?

Whatever the manufacturer printed next to the valve. That is not a dodge — it is now the rule in college soccer.

The NCAA's 2024 and 2025 rules changes rewrote Rule 2.1.3 to read: "The pressure of the ball shall be 8.5 to 15.6 psi. Ball pressure shall conform to the manufacturer's recommendation." The committee's reason was that "various manufacturers have different ball pressure requirements printed on the ball," and that deferring to them would "avoid potential injury situations where the ball is inflated above the manufacturer's recommendation."

So what do manufacturers recommend? Select, whose balls carry FIFA quality marks, publishes its ranges by size and ball type:

Three things jump out. A size 3 is recommended as low as 5.8 psi, well under the Law's 8.5 psi floor, because that floor was never written for a size 3. A club size 5 and a pro size 5 get different ranges despite being the same size. And nothing is recommended near 15.6 psi — the top of the legal window is a limit, not a target.

So when a chart says "8.7 psi for sizes 3, 4 and 5," it is taking the bottom of the Law's size-5 range and applying it to balls the Law does not describe. On a size 3, 8.7 psi is the ceiling of what Select suggests.

The practical rule: find the embossed range near the valve, aim at the lower half of it, and ignore any chart that disagrees with the ball in your hands.

Can you over-inflate a soccer ball?

Easily, and it is the more common error by a wide margin — a hand pump with no gauge passes 15 psi faster than most people expect. An over-inflated ball is harder, bounces higher and longer, is less predictable off a young player's first touch, and strains the seams and bladder inside it.

England's Football Association puts it in its headline bullets. The FA's heading guidance lists, alongside its age-by-age heading limits: "Don't over inflate the footballs: use the lowest pressure authorised by the Laws of the Game."

Under-inflation is a real problem too — a soft ball is heavy off the foot and travels short — but it rarely happens at the pump. It happens over weeks of nobody checking.

Does ball pressure affect heading?

This is why governing bodies started talking about pressure at all, and the honest answer is "probably a little, and not reliably."

UEFA's 2020 youth heading guidance recommended reducing ball pressure to "the lowest pressure authorised by the laws of the game." That recommendation was finally tested in 2025: England and colleagues at Loughborough University, in Annals of Biomedical Engineering, fired two match balls at an instrumented Hybrid III head and neck at 0.6 bar and 1.0 bar across 34 permutations of impact location, head orientation and neck angle. In their results, impact magnitude decreased in 82% of impacts and was unchanged in another 8%, with average changes of −2% to −12%. But 10% got worse, and the authors concluded that while reduced pressure was "overall an effective mitigation," it "is not a universal solution."

A 2024 systematic review in the Journal of Functional Morphology and Kinesiology, written by staff at the United States Soccer Federation, found only nine studies on the whole question. Their summary: "reducing inflation pressure may decrease impact magnitude," lower ball mass means lower impact, and — a detail that earns its place in a wet November — two studies found "wet balls were heavier and had greater impact forces than dry balls." The reviewers called for more controlled research.

So softer is a sensible default that costs nothing, but it is a modest effect with exceptions, not a safety device. What actually governs your child's heading exposure is their age group's rules, set out in our guide to youth soccer heading rules by age, and the limits their coach applies in training.

Does cold weather deflate a soccer ball?

Yes, and by more than most people assume. Nothing leaks — the air inside simply contracts.

Pressure in a sealed, roughly fixed-volume ball rises and falls with absolute temperature. To size the effect, add atmospheric pressure (about 14.7 psi) to the gauge reading, scale by the ratio of the two temperatures in Kelvin, then subtract the 14.7 again. Inflate indoors at 70°F and this is roughly what the gauge reads at kickoff:

A ball set to 12 psi in a warm house loses about 1.9 psi by the time it is sitting on a frozen field. More striking: a size 5 ball set to 8.7 psi indoors — a legal, sensible number — reads about 7.0 psi at freezing, under the Law's own minimum.

Two things follow for the winter months. Check pressure at the field, in the cold, not in the car. And check it before the ball has been warmed up by twenty minutes of play, because kicking heats the air inside and nudges the reading back up.

The same cold is working on your player; what to put on them is in our guide to soccer in cold weather.

Why does my soccer ball keep going flat?

If it loses pressure over days rather than minutes, that is usually normal rather than a fault.

• Bladder type. Latex bladders feel softer and leak air steadily through the material itself; butyl holds pressure far longer. A cheap ball going soft in a fortnight is often behaving exactly as built.
• A dry or bent needle. Pushing an unlubricated needle into the valve tears it, and a torn valve leaks forever. Wet it, and push it straight.
• Cold storage. A ball left in a trunk reads low in the morning and comes back up indoors. That is temperature, not a leak.
• Water. A ball that sat in puddles is heavier rather than flatter — construction and water resistance are what the FIFA quality marks actually test for.

Inflating it well is four habits: read the printed range first, wet the needle every single time, stop early and gauge it rather than guessing, and recheck at the field in the temperature the game will be played in. The step-by-step version is below.

What this means for the team ball bag

1. The printed range on the ball beats every chart, including this one. Aim at the lower half of it.
2. Cold costs you one to three psi. Set pressure where the game is, not where the pump is.
3. Softer is the better default for young players — guidance and biomechanics point the same way, even if the effect is modest.

A correctly inflated ball is also the one that rewards technique: a rock-hard ball bounces off a nine-year-old's instep and teaches them nothing about receiving. FlickTec's home sessions, built by a UEFA Pro Licence coach, are built around that first touch — with whatever ball is in the garage.

Frequently Asked Questions

How much air should a size 4 soccer ball have?

There is no official figure — Law 2's 8.5–15.6 psi range describes a size 5 match ball, and the Laws say nothing about size 4. Go by the range printed on the ball. Select, for example, recommends 0.5–0.7 bar (7.3–10.2 psi) for its size 4 balls, noticeably below the size-5 legal minimum.

What psi should a size 5 soccer ball be?

Between 8.5 and 15.6 psi to satisfy Law 2, but aim well below the top of that window. Manufacturers' own recommendations for size 5 sit around 0.6–0.9 bar (8.7–13.1 psi) for club balls and 0.7–1.0 bar (10.2–14.5 psi) for professional match balls. The NCAA now requires college balls to conform to the manufacturer's printed recommendation as well as the psi range.

Does cold weather deflate a soccer ball?

Yes. The air inside contracts as it cools, so pressure drops without anything leaking. A ball inflated to 12 psi at 70°F reads roughly 10 psi at freezing — about 1.9 psi lower. A ball set near the legal minimum indoors can fall below it outdoors. Check and set pressure at the field, in the cold, before play has warmed the ball up.

Can you over-inflate a soccer ball?

Yes, and it is the more common mistake with a gauge-less pump. An over-inflated ball is harder, bounces unpredictably and stresses the seams and bladder; the NCAA cited avoiding injury situations caused by inflating above the manufacturer's recommendation when it tied its rule to the printed range. England's FA advises outright: "Don't over inflate the footballs: use the lowest pressure authorised by the Laws of the Game."

Does a softer ball make heading safer?

A little, and not consistently. A 2025 study in Annals of Biomedical Engineering found that dropping a match ball from 1.0 bar to 0.6 bar reduced head impact magnitude in 82% of laboratory impacts and left another 8% unchanged, with average reductions of 2–12% — but 10% of impacts increased, and the authors concluded reduced pressure "is not a universal solution." A 2024 US Soccer-authored review found only nine studies on ball characteristics and heading and called for more controlled research. Treat lower pressure as a free, sensible default rather than a protective measure.