The short answer: most golf balls are a rubber core, usually polybutadiene, wrapped in one or more layers and a cover. A two-piece ball has a big core and a tough ionomer cover. Premium balls add a mantle layer and a thin, soft urethane cover. The cover carries 300 to 500 dimples that cut drag, and a driver is in contact with the ball for only about 0.0004 seconds.
This article goes with episode 1 of HYTON Golf, our video series that cuts golf open in 3D. Every fact below is linked to its source at the end.
Key numbers
| Number | What it means | Source |
|---|---|---|
| 1.680 in | Smallest diameter a golf ball may have under the Rules of Golf | R&A Rules of Equipment, Part 4 |
| 1.620 oz | Most a golf ball may weigh | R&A Rules of Equipment, Part 4 |
| 300 to 500 | Dimples on most golf balls | Scientific American |
| About 0.010 in | Typical dimple depth | Scientific American |
| About half | How far a smooth ball would fly compared with a dimpled one | Scientific American |
| About 400 µs | How long a driver stays in contact with the ball | Roberts, Jones and Rothberg (2001) |
More numbers from the series, each with its source: Golf by the Numbers.
Watch the episode: What's Actually Inside a Golf Ball? on YouTube (2:46).
The rules: how big and how heavy
Under the USGA and R&A equipment rules, a conforming ball can't be smaller than 1.680 inches (42.67 mm) across and can't weigh more than 1.620 ounces (45.93 g). Every ball you're allowed to play in competition fits inside those two numbers.
Inside a two-piece ball: the core and the cover
The simplest modern ball has two pieces. The core is usually a synthetic rubber called polybutadiene. It is the engine: when the club squashes it, it springs back and fires the ball off the face.
On most budget balls the cover is an ionomer, a hard, cut-resistant plastic. Firmer covers tend to spin less, which can keep drives a little straighter. The catch is that they don't stop as quickly on the green.
Multi-layer balls: the mantle and the urethane cover
Premium balls add layers: three, four, even five pieces. Between the core and the cover sits a mantle, a layer engineers use to fine-tune speed, spin and feel. On the outside is a thin, soft urethane cover, soft enough that the grooves on a wedge can grab it. That is where short-game spin comes from.
So every ball is a trade-off: a firm, simple ball for distance and durability, or a layered ball with a soft skin for control around the greens.
Impact: about 400 microseconds
When a driver hits the ball, the two are in contact for about four ten-thousandths of a second. Researchers at Loughborough University measured around 400 microseconds. In that instant the ball flattens against the face and springs back, and its speed, launch and spin are all decided.
Why golf balls have dimples
Most golf balls have between 300 and 500 dimples, each only about a hundredth of an inch deep. Back in the 1800s, golfers noticed that beat-up old balls flew better than smooth new ones. They were onto something.
Dimples trip the air into a thin, turbulent layer that clings to the ball a little longer, so the wake behind it gets smaller. Smaller wake, less drag.
According to golf ball scientists quoted in Scientific American, a smooth ball hit by a pro would travel only about half as far.
Illustrations by HYTON. Layer thicknesses are approximate.
Sources
- R&A Rules of Equipment, Part 4 (Conformance of Balls), Rules 4.2 and 4.3: maximum weight 1.620 oz (45.93 g), minimum diameter 1.680 in (42.67 mm); the USGA applies the same limits
- GOLF.com, Understand golf ball construction: cores, mantles, ionomer and urethane covers
- US Patent 9,415,270 B2 (background section): polybutadiene cores; ionomer and polyurethane covers
- Roberts, Jones and Rothberg (2001), Loughborough University: driver contact time of about 400 microseconds
- Golf Heritage Society, Collecting golf balls: featheries and gutta percha: golfers found that scratches and dents on gutta percha balls straightened their flight
- Scientific American, How do dimples in golf balls affect their flight?: 300 to 500 dimples about 0.010 in deep; turbulent boundary layer and smaller wake; a smooth ball would fly about half as far
Sources last checked October 2026.
Frequently asked questions
How many layers does a golf ball have?
Two or more. The simplest modern balls have two pieces: a large rubber core and a cover. Premium balls usually have three, four or five pieces, with one or more mantle layers between the core and the cover.
What is the core of a golf ball made of?
Usually a synthetic rubber called polybutadiene. The core stores energy when the club compresses it and springs back to launch the ball.
What is the difference between an ionomer and a urethane cover?
Ionomer is a harder, cut-resistant plastic common on two-piece balls; firmer covers tend to spin less. Urethane is a thinner, softer cover used on many premium balls, so wedge grooves can grip it for more short-game spin.
How long is a golf ball on the clubface?
About 400 microseconds, or 0.0004 seconds, for a driver, based on measurements by researchers at Loughborough University (Roberts et al., 2001).
How many dimples does a golf ball have?
Most golf balls have between 300 and 500 dimples, each about 0.010 inch deep, according to golf ball scientists quoted in Scientific American.
Would a smooth golf ball fly as far?
No. According to the same Scientific American article, a smooth ball hit by a pro would travel only about half as far as a dimpled one, because dimples reduce drag.
From this episode
The cutaway from this episode is on the Anatomy of a Golf Ball Accent Mug ($18.99): the cover, mantle and rubber core, each labeled, with the dimples and the size and weight limits from the rules. It comes with a navy, black or light blue handle and interior, printed to order with free US shipping. More designs from the series are in the Wear the Science collection.