Understanding MOI

Moment of Inertia (MOI) has been a hot topic in golf marketing lately, especially for drivers and putters. Simply put, MOI measures how much a clubhead resists twisting when you hit the ball off-center. The higher the MOI, the more forgiving the club—keeping the face square at impact even if you miss the sweet spot. Think of it like a figure skater: arms out wide (high MOI) makes spinning tougher; arms in (low MOI) makes it easier.

MOI and the USGA

The USGA tests MOI around the vertical axis through the clubhead’s center of gravity, using a jig set at a 60-degree lie angle. They’ve capped this MOI at 5,900 g·cm² for drivers, with a 100 g·cm² tolerance, to keep the game challenging. This test focuses on how the club resists twisting side-to-side on mis-hits.

Manufacturers and Marketing

While the USGA sticks to one axis, manufacturers often measure MOI across multiple axes—like vertical and horizontal—for a fuller performance picture. This can lead to marketed values higher than the USGA’s limit, like 10,000 g·cm² (the magic 10K MOI figure), without breaking rules. These numbers reflect combined axes, not just the regulated vertical one, so it’s worth clarifying what you’re comparing.

Why It Matters

For golfers, higher MOI means more forgiveness, especially on those not-so-perfect shots. It’s a big deal for consistency, making it a key spec to check when picking out a driver or putter. Just know the difference between the USGA’s limit and a brand’s broader claims, and you’ll be better equipped to find the right club for your game.

Review the real testing procedure here USGA-TPX3005.