What Size Are Golf Balls?

A golf ball is one of the most engineered pieces of sporting equipment, yet its size is governed by a surprisingly simple rule: a regulation golf ball must be at least 1.68 inches in diameter. This precise measurement is the launching point for a fascinating story of regulations, physics, and performance. This article explains not just the exact size of a golf ball, but why that size exists, how it affects your shots, and what you should really be looking for when you open up a new sleeve.

The Official Rules: Getting to the Point on Golf Ball Size

For a golf ball to be legal for tournament play, it has to meet the standards set by golf's two governing bodies, the USGA (United States Golf Association) and The R&,A (based in St Andrews). While their rule books are thick, the specifications for the golf ball itself are refreshingly straightforward.

Here are the two fundamental requirements:

• Diameter: A golf ball must not have a diameter smaller than 1.68 inches (42.67 mm). There is no maximum size, but engineering constraints for performance mean they all effectively stick right at this minimum.
• Weight: A golf ball must not weigh more than 1.62 ounces (45.93 g). There is no minimum weight limit, but once again, performance engineering keeps all balls near this maximum a reality.

Beyond these two core rules, there are other important regulations that ensure fairness. One is the requirement for "spherical symmetry." This means a golf ball must fly the same way no matter how it’s oriented or spun. This rule was famously enacted to outlaw the Polara ball from the 1970s, which had unique dimples that self-corrected hooks and slices. In essence, a ball has to be truly round and behave consistently.

Manufacturers also submit their balls for testing to ensure they don’t fly too far under standardized test conditions, known as the Overall Distance Standard (ODS). This "speed limit" keeps the game from being overpowered entirely by technology.

A Tale of Two Golf Balls: How We Got to 1.68 Inches

That 1.68-inch number might seem arbitrary, but it was the winner of a long-standing debate in the golf world. For much of the 20th century, there wasn't one single golf ball standard. There were two.

The "British" Ball (or "Small Ball")

Played primarily in countries under The R&,A's governance, this ball had a minimum diameter of just 1.62 inches - the same as today's maximum weight in ounces. Because it was smaller and had less surface area, many players felt it bored through the wind more effectively and was sometimes easier to control on the ground. Its smaller size made the hole look bigger, which some thought was a mental advantage on the greens.

The "American" Ball (or "Large Ball")

The USGA mandated a larger ball with the 1.68-inch diameter we use today. This larger ball presented more surface area to be acted upon by the air. It tended to fly higher, which made it easier for average players to get airborne and hold greens on approach shots. Most American amateurs grew up playing this ball and were comfortable with its flight characteristics.

This difference created fascinating strategic choices. American pros playing in The Open Championship would often switch to the smaller British ball to gain an advantage in the links-style wind, while British players might struggle to adapt to the "floater" nature of the American ball when playing in the U.S.

Then, in 1990, The R&,A made a change to unify the game. They phased out the smaller ball and officially adopted the 1.68-inch USGA standard for all play, establishing a single global rule for golf ball size that we've had ever since.

Why Does That Tiny Difference Matter? The Physics Behind the Rules

While all conforming balls today are the same size, understanding why this specific size and weight work is a great window into the physics of a golf shot. It’s not just a random number, it's a foundation that affects everything.

The Aerodynamics of Takeoff

Think of the 1.68-inch surface area as the canvas for a highly technical art form: dimple design. A golf ball without dimples would fly like a knuckleball, tumbling through the air and dropping like a stone. Dimples are what give a ball its lift and predictable flight.

Here’s how it works in simple terms:

• Lift: The backspin you impart on the ball at impact grips the air. The dimples create a thin layer of turbulent air that clings to the ball's surface. Air moving over the top of the spinning ball travels faster than the air moving underneath it, creating a pressure difference (lower on top, higher on bottom). This difference generates an upward force called lift, keeping the ball in the air longer.
• Drag Reduction: A smooth ball creates a large pocket of low-pressure air behind it as it flies, which acts like a suction cup pulling it backward. The dimples stir up the air, creating that turbulent layer which reduces the size of this vacuum, cutting down on drag and helping the ball maintain its speed.

The 1.68-inch standard provides a consistent, large enough surface for aerodynamic engineers to perfect dimple patterns that optimize this lift-to-drag ratio for maximum distance and control.

Inside the Sphere: What's Really Packed into 1.68 Inches

As a golfer, you can take comfort knowing any sleeve of balls from a major brand will meet that 1.68-inch rule. This effectively takes ball size out of your decision-making equation. The real question is not "What size ball should I play?" but "What's inside that ball?"

Since the external dimension is fixed, the true innovation happens inside. Here’s a breakdown of what makes one conforming ball different from another.

The Core: Your Ball's Engine

The rubber core is the largest component and the primary source of a ball’s speed. The main difference here is compression - a measure of how much the ball deforms at impact.

• Low-Compression Cores: These are softer and feel "gentle" off the clubface. They are designed for golfers with slower to moderate swing speeds (typically under 90 mph). The softer core allows these players to fully "compress" the ball at impact, maximizing energy transfer for a spring-like effect that boosts distance.
• High-Compression Cores: These are much firmer and require higher swing speeds (typically over 105 mph) to deform. For a fast swinger, a firm core provides a more solid, controlled energy transfer that translates into immense speed without feeling "mushy."

The Mantle Layers: The Transmission

Sandwiched between the core and the cover, one or more mantle layers help refine how the ball performs. These layers act as a bridge, influencing spin rates on different types of shots. For example, a mantle can be designed to reduce spin off the driver (for more distance and straighter shots) while still allowing the cover to generate high spin on short irons and wedges for stopping power.

The Cover: Where Feel Meets Spin

The outermost layer is what you feel and what interacts with the grooves of your wedges. There are two main types:

• Urethane Covers: Found on premium, "tour-level" balls (like the Titleist Pro V1 or TaylorMade TP5). Urethane is a soft, sticky material that grabs the clubface on short shots, generating immense greenside spin. It offers the best overall performance and feel but is less durable and more expensive.
• Ionomer (often "Surlyn") Covers: Found on most distance and "value" balls. Ionomer is a firm, durable plastic that spins less, particularly on driver shots, which can help reduce hooks and slices. It’s incredibly resilient to cuts and scuffs and is more affordable, but it won’t give you the bite or soft feel of a urethane ball around the greens.

Your job as a player isn’t to worry about the size, but to find the right combination of core, mantle, and cover that matches your swing speed and what you want the ball to do.

Conforming vs. Non-Conforming: The Outliers

While 99% of balls for sale are conforming, you might occasionally see balls marketed as "non-conforming" or "illegal." These balls deliberately ignore the USGA/R&A rules to offer a specific, often humorous, performance advantage. These include:

• Overly Long Balls: Designed with core and dimple patterns that exceed the Overall Distance Standard. They go farther but are banned in competition.
• Slice-Correcting Balls: Similar to the old Polara, these balls have unique construction or dimple patterns that reduce sidespin.
• Oversized Balls: Larger than the 1.68-inch standard, these can be easier for beginners, juniors, or seniors to make solid contact with, making them great training tools or just-for-fun options.

You cannot use these in a tournament or even to post an official handicap score, but they can be a fun way to enjoy a casual round.

Final Thoughts

So, the technical answer to "what size is a golf ball?" is pretty simple: no less than 1.68 inches in diameter. But as we've seen, that standard size is the foundation for incredible engineering. Your focus shouldn't be on the external measurement, but rather on the internal construction - the core, cover, and compression - that defines how a ball will perform for your unique swing.

Choosing the right ball from the hundreds of options can feel overwhelming. While they are all the same size, their flight, spin, and feel are worlds apart. It’s what inspired us to build a more direct way for you to find answers. Using Caddie AI, you can ask specific questions like, "What type of golf ball is best for a player with a 95 mph swing speed who wants more wedge spin?" and get a personalized recommendation in seconds. We help you sort through the noise so you can find the perfect ball and play with more confidence.