You’ve probably heard a lot about the term 'MOI' in golf lately, especially when it comes to new drivers and putters.

This acronym stands for “moment of inertia.” Its importance relates to how forgiving a club may or may not be. Relatively speaking, the better the player you are, the less 'MOI' you might need since you’re capable of hitting a smaller sweet spot on the club face than high handicap players. 

But that’s really an over-generalization of a complicated thing. "MOI" measures how much resistance a clubhead has to twisting (in terms of grams per centimeter squared). The higher the MOI, the more resistance a club exhibits, meaning the more forgiving the club will play.

Better players like forgiveness, too, especially in their drivers. It’s not just about hitting it straight, either. It's also about not losing much distance on off-center hits. Distance plus relative straightness is a great combination off the tee, no matter what level player you are. 

The scoring clubs like wedges and short irons can be a different story for better players. That's where feel can be so important. The same goes for certain players when it comes to putters. (Scotty Cameron blade putters, for example, offer feel that might be the most important part of the equation for skilled players). But many of the best players in the world do often opt for maximum MOI putters like TaylorMade Spider or the Odyssey AI One putters. Yes, artificial intelligence is playing a role in MOI designs now, too. (More on that in a bit).

First, let’s talk about MOI (moment of inertia), and what it means. Moment of inertia is obviously not limited to golf clubs, but why is it so important in golf and what is MOI in golf?

The actual formula in physics for MOI is a bit complicated. But basically, according to thoughtco.com, “for any rotating object, the moment of inertia can be calculated by taking the distance of each particle from the axis of rotation, squaring that value, and multiplying it times the mass of that particle. You do this for all of the particles that make up the rotating object and then add those values together, and that gives the moment of inertia.”

So essentially, in golf, MOI is a measure of how resistant the clubhead is to twisting when it strikes the golf ball. The more resistant to twisting, the higher the MOI. 

Many of the new drivers on the market are being billed as the highest MOI drivers to date. And some of these companies like TaylorMade and Callaway are using artificial intelligence to design clubs with the highest MOI possible. 

TaylorMade’s latest driver, the Qi10 Max, is named for its MOI reading of 10,000 units. According to TaylorMade: “Because we're golfers and not physicists, it's all about stability and forgiveness at impact. When we say Qi10 Max boasts 10K MOI, we're not just throwing around
numbers – we're defining a new frontier of forgiveness.”

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What gives a golf club high MOI is found mostly in the head design. In simple terms, the more weight club manufacturers can distribute away from the center of gravity or the sweet spot, the less resistance there is to twisting and the higher the MOI. While high MOI is most talked about in modern drivers and putters these days, the concept of perimeter-weighted irons, pioneered by Ping decades ago, is also good example of increasing the MOI in irons. 

For years, most pros played forged blades, which is a lower MOI club, while amateurs generally played cavity back irons. In recent years, however, the concept of "players" clubs has emerged. These designs, like the TaylorMade 790s, are hollow, often with material inserted in them and weight in the perimeter, though that might not be apparent in their appearance. This is what gives them a “players” look and feel but the forgiveness of a cavity back. 

Most drivers these days have added weight in the heel, toe and sole. For many modern drivers, these weights are adjustable. So if you have a tendency to slice, putting more weight near the heel will help the club face close faster. Putting more weight in the toe will slow down the closing of the club face, which will promote a slightly open club face. The latter is best for the minority of players who tend to fight a true hook. If you have a tendency to slice, then moving weight to the draw configuration with more weight in the heel could be beneficial.

You can see these same characteristics in putters. Old blade putters were very unforgiving. Golfers, especially high handicap players, aren’t especially good at finding the sweet spot consistently when they putt. So adding weight to the heel and toes on a putter can definitely help. 

For the highest MOI, however, you want a mallet putter. Simply put, a mallet allows more opportunity to distribute weight to make it more stable, which is what high MOI provides. Some of these putters have interchangeable weights so you can increase or decrease the overall weight and MOI depending on your preference. There has also been a tendency in recent years to design putters that are heavier overall, which also increases MOI. A super heavy putter, for example, isn’t going to twist much when it strikes a golf ball going just a few miles per hour.

How do you know how much MOI is right for you? The short answer is you should probably get as much as your game allows. However, many players don’t like clunky looking irons, for example, or even a clunky putter. How a club looks and feels is important when it comes to conveying confidence. 

But numbers don’t lie. Even if you like the way one club looks from another, if you go through a thorough fitting process, you can get a pretty good picture of what performs better for you. A less attractive club with great numbers can suddenly seem a lot more attractive. And it’s not just about overall distance. Accuracy and distance control are very important measurements to consider. 

For example, if you’re a single-digit handicap, you might like the way the Titleist muscle back irons set up and feel. But again, they are a lower MOI club; they’re not going to be that forgiving. A fitting might confirm that a better choice could be the new T-150s, which have tungsten weighting built in. The weights not only increases MOI, but also helps get the ball to spin in the air better. Maybe you need that help; maybe you don't. A fitting is a great way to confirm that.

If you’re a player who likes to work the ball right to left or left to right or both ways, you probably don’t want high MOI, which inhibits your ability to do so. A great example is the popularity of the new mini-drivers, which have heads that are much smaller than the current USGA limit of 460cc. They have less MOI and more loft, and are going to allow you to work the ball off the tee more. Tommy Fleetwood and Adam Scott are among the PGA Tour players who regularly hit mini-drivers, which are gaining popularity among better players.

The bottom line is that there are lots of choices out there. Enlist the help of a golf professional to help you make the best selections. MOI could be your best friend.

• MOI, or Moment of Inertia, in golf clubs refers to a clubhead’s resistance to twisting when the ball is hit off-center, where higher MOI provides more stability, consistency and ‘forgiveness’ for off-center hits. This is particularly valuable for amateur golfers who mishit a lot of shots.
• Obviously not all golf clubs have a high MOI. For example, persimmon drivers back in the day had a low MOI, but there were some benefits to that as well because the head design had something called a gear effect. If you hit it off the toe, for example, the club face might open up. But because of the roll and bulge of the design of the head, they tended to hook back into play. The same effect would happen with a heel shot. It would curve the other way. Low MOI also made these clubs very easy to work from right to left or left to right. When a club is very unforgiving, off-center shots meant a lot less ball speed, too. 
• Custom golf club fitting can be important to determine how much MOI a player needs. But again, you might be surprised to see how many scratch to plus-handicap players opt for drivers with the highest possible MOI. You have to weigh any desire to work the ball with overall forgiveness. Off the tee, it seems, forgiveness might be king.