Choosing the correct shaft flex is one of the most critical components of a golf club fitting. The "flex" refers to the ability of a golf shaft to bend as forces are applied to it during the swing. If your shaft is too stiff, you may lose distance and struggle with a "slice" (the ball fading to the right for right-handed players). If it is too soft (too flexible), you might experience an inconsistent "hook" or high, ballooning shots.
The Primary Metrics
Swing Speed: Generally measured with a driver. Faster speeds require stiffer shafts to keep the clubhead stable at impact.
Carry Distance: If you don't know your speed, your average carry distance is a reliable proxy.
Tempo: This is how quickly you transition from the top of your backswing to the downswing. A violent or "aggressive" transition creates more load on the shaft, often requiring a stiffer profile even if the raw speed isn't elite.
General Shaft Flex Ranges
Flex Designation
Swing Speed (MPH)
Carry Distance (Yards)
Ladies (L)
Under 75
Under 180
Senior/Lite (A/M)
75 – 85
180 – 210
Regular (R)
85 – 95
210 – 240
Stiff (S)
95 – 105
240 – 275
Extra Stiff (X)
Over 105
Over 275
Practical Example
Suppose a golfer has a 92 mph swing speed. Based on speed alone, they fall into the "Regular" flex category. However, if that golfer has a very aggressive tempo and quick transition, they might benefit more from a Stiff shaft to prevent the clubhead from lagging too far behind or oscillating too much.
function calculateShaftFlex() {
var speed = parseFloat(document.getElementById('swingSpeed').value);
var carry = parseFloat(document.getElementById('carryDistance').value);
var tempo = document.getElementById('swingTempo').value;
var finalSpeed = 0;
// Determine effective speed
if (!isNaN(speed)) {
finalSpeed = speed;
} else if (!isNaN(carry)) {
// Approximate conversion: Speed = Carry / 2.3
finalSpeed = carry / 2.3;
} else {
alert("Please enter either your Swing Speed or Carry Distance.");
return;
}
// Adjust for tempo (Aggressive tempo adds virtual load/speed)
if (tempo === "aggressive") {
finalSpeed += 5;
} else if (tempo === "smooth") {
finalSpeed -= 3;
}
var flex = "";
var desc = "";
if (finalSpeed = 75 && finalSpeed = 85 && finalSpeed = 95 && finalSpeed < 105) {
flex = "Stiff (S)";
desc = "A Stiff flex shaft is recommended. This helps stabilize the clubhead through impact for higher speeds, preventing the ball from ballooning or hooking excessively.";
} else {
flex = "Extra Stiff (X)";
desc = "Your high swing speed requires an Extra Stiff shaft to maintain control and minimize shot dispersion. This stiffer profile will keep up with your aggressive power.";
}
document.getElementById('flexValue').innerText = flex;
document.getElementById('flexDescription').innerText = desc;
document.getElementById('golfResult').style.display = 'block';
document.getElementById('golfResult').scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}