Golf Shaft Flex Chart: Speed, Tempo and the CPM Numbers Behind L, A, R, S and X
Under 84 mph of driver speed, start at Senior/A. From 84 to 100 mph, Regular. From 101 to 113, Stiff. Above that, X. Then adjust one step firmer if your transition is aggressive and one softer if it is smooth. The letters are not standardised between brands, so the chart below also gives CPM, weight and torque ranges so you can compare two shafts that both say 'S'.
By the All Birdies Editorial Team
Start here: under 84 mph of driver swing speed, Senior/A flex. From 84 to 100 mph, Regular. From 101 to 113, Stiff. Above 113, X. Then move one step firmer if your transition from backswing to downswing is abrupt, and one step softer if it is unhurried.
That two-variable answer gets most golfers to the right shaft. What it does not do is survive contact with a shop wall, because the letter on a shaft is not a standardised measurement. An 'S' from one manufacturer can measure 20 cycles per minute softer than an 'S' from another, which is a full flex of difference wearing the same badge.
So the chart below has two halves. The first picks a flex from your speed and tempo. The second gives the frequency, weight and torque ranges behind each letter, which is what you actually compare when two shafts disagree with each other.
Flex is a frequency, not a letter
Clamp a shaft at the butt, hang a weight on the tip, pluck it and count how many times it oscillates per minute. That number, CPM, is what flex means. A higher CPM is a stiffer shaft.
There is no governing body for the letters. No standards organisation defines Regular. Each manufacturer sets its own ladder, and the good ones publish frequency data while the rest publish a letter and a colour.
This is why the single most useful thing you can do in a fitting bay is ask for the frequency of the shaft you are testing. If your current gamer is 248 CPM and the new one is 265, you have a real comparison. If your current gamer is 'R' and the new one is 'R', you have nothing.
The selection matrix
Enter on driver swing speed if you have it measured, or on honest 6-iron carry if you do not. Then read across to the tempo column that describes you.
Driver swing speed 6-iron carry Smooth, late transition Average tempo Aggressive, early load Under 72 mph Under 105 yards L (Ladies) L L, or a soft A 72-83 mph 105-125 yards L, or a soft A A (Senior) A, or a soft R 84-92 mph 125-142 yards A, or a soft R R (Regular) R 93-100 mph 142-158 yards R R R, or a soft S 101-107 mph 158-172 yards R, or a soft S S (Stiff) S 108-113 mph 172-185 yards S S S, or a soft X 114 mph and up 185+ yards S, or a soft X X (Extra Stiff) X, or TX If two cells in your row disagree, take the softer one. An over-stiff shaft is a harder fault to play around than an over-soft one. The 6-iron carry column is there because most golfers do not know their swing speed and half of those who claim to are quoting a number a friend read off a launch monitor five years ago. A carry distance you have measured over ten shots is better data than a speed you half-remember.
Notice how much overlap there is between adjacent rows. That is honest. Flex selection has a genuine tolerance of about one step, and inside that step the shaft's weight and profile matter more than the letter.
Tempo, the second variable
Two golfers at identical 98 mph can need different shafts, and the reason is how quickly they load it.
A player who starts down gently and accelerates late puts less peak bending force into the shaft. A player who snaps the transition, the classic hit-from-the-top pattern, loads the shaft hard and early and will bend a Regular into a hook.
You can measure this crudely. Film your swing at 240 frames a second on a phone and count frames from the top of the backswing to impact. Under about 60 frames, roughly a quarter of a second, is a fast transition. Over about 80 is a slow one. The well-known tour ratio of roughly three-to-one, backswing to downswing, is the reference point.
The practical instruction: if you know you are a snapper, ignore the middle column of the matrix and take the right-hand one.
CPM, weight and torque by flex
Ranges rather than points, because the overlap is the whole reason this section exists. Driver figures are quoted at a standard butt clamp; iron figures are for a 6-iron and step up roughly four to five CPM per club as you go shorter.
Flex Driver CPM 6-iron CPM Typical driver shaft weight Typical torque Profile note L (Ladies) 195-215 250-270 40-50 g 5.5-7.0° Soft tip, high launch, high spin by design A / M (Senior) 215-232 265-285 45-58 g 4.8-6.0° Still tip-soft; the most useful flex in club golf and the least sold R (Regular) 232-252 280-300 50-65 g 4.0-5.5° Widest internal variation of any flex letter S (Stiff) 252-268 295-315 60-75 g 3.0-4.5° A soft S from one brand overlaps a firm R from another X (Extra Stiff) 265-285 310-330 70-85 g 2.0-3.5° Buying X because it sounds better is the most common fitting error TX / 6.5 and above 280+ 325+ 75-90 g 1.7-3.0° Genuine tour speed only, above roughly 118 mph Look at the overlaps: 265 CPM appears in both the S and X rows. That is the whole argument for asking for frequency instead of a letter. Torque is the shaft's resistance to twisting, measured in degrees, and it is the specification most often misread. Lower torque is not automatically better. A low-torque shaft in the hands of a 90 mph player feels boardy and dead, and does nothing for dispersion because that player is not generating the twisting force the shaft was built to resist.
Weight is the specification that changes ball flight most and gets discussed least, which is the subject of a section further down.
What mis-flexing actually costs
Symptom Likely cause Direction of the miss Launch and spin effect First fix to try Ball balloons, distance collapses in any wind Shaft too soft for your load Left for a right-hander, hook bias +2 to 4° launch, +300 to 700 rpm One flex firmer, or the same flex in a firmer tip profile Low, weak flight with a fade that becomes a block Shaft too stiff Right for a right-hander -2 to 3° launch, and a strike that drifts low on the face One flex softer, or the same flex 10 g lighter Two-way dispersion with no pattern Usually weight, not flex Both Variable Change shaft weight before touching flex Good numbers on the range, no control on the course Tempo speeds up under pressure Left Higher spin than in testing Fit to your fast tempo, not your comfortable one Feels right at 80% and unhittable at full effort Shaft is at the top of its load range Left Spin spikes on the hardest swings One flex firmer Two shafts marked the same letter feel entirely different No industry flex standard n/a n/a Compare CPM and weight, ignore the letter Match your symptom in column one, then change one variable at a time and re-test. Changing flex and weight together tells you nothing. Weight before flex
Most golfers over-index on flex and ignore shaft weight, and it is the wrong way round. A 65-gram Regular and a 50-gram Regular will produce noticeably different ball flights, different tempos and different strike patterns from the same swing.
Heavier shafts tend to slow the transition slightly, which for an aggressive player is a genuine benefit rather than a distance cost. Lighter shafts give speed to golfers who have none to spare, at the price of a strike pattern that spreads out.
A useful sequence in a fitting bay: settle weight first by hitting three shafts of the same flex at 50, 60 and 70 grams, pick the one where your strike tightens, then adjust flex inside that weight. Most fitters work this way already, and if yours starts by handing you an X-stiff because you look strong, find another fitter.
The same logic applies to iron shafts, where the steel-versus-graphite decision is really a weight decision wearing a material label. A 95-gram graphite iron shaft and a 95-gram steel one behave far more alike than a 95-gram steel and a 130-gram steel.
Where the Rules touch shafts
Very little of shaft fitting has a legality dimension, but three points do, and one of them catches people out.
The shaft itself must be straight from the top of the grip to a point five inches above the sole, and must bend and twist the same way in every direction. Nothing on sale from a mainstream manufacturer fails this. It exists to rule out engineered kick patterns and hinged designs.
Re-shafting does not affect a driver head's conforming status. The head is what appears on the List of Conforming Driver Heads, and swapping the shaft leaves that untouched.
Length is where a re-shaft can create a problem. Fit a 46-inch shaft to gain speed and you clear the 48-inch limit in the Equipment Rules comfortably, but you are exactly at the 46-inch ceiling of Model Local Rule G-10, and a build at 46.5 puts you the wrong side of it in any competition that has adopted G-10. If you compete, spec the build at 45.75 and stop worrying about it.
One more, which people trip over at the turn: adjustable hosels count as adjustable features under Rule 4.1a(3). You may not deliberately change a club's characteristics during a round. Making a stroke with a club so adjusted is a disqualification.
Checking your own flex without a fitting bay
- Look at where the wear mark sits on your driver face. Persistently high-toe with a left miss usually means too soft; persistently low-heel with a right miss usually means too stiff.
- Hit ten 6-irons and record the carry spread. A spread wider than about 12 yards with clean strikes points at the shaft rather than at you.
- Ask any decent shop to frequency-check your current gamer. It takes two minutes and gives you the one number worth carrying into every future purchase.
- Compare like with like: the same flex letter in the same model line is consistent; across brands it is not.
- If you are between two flexes and cannot decide, take the softer shaft in the heavier weight. It is a more forgiving combination than the reverse.
- Re-check after a winter of no golf, and after any season where your speed changed by more than about 4 mph in either direction.
A final opinion, offered plainly because the industry will not: most club golfers playing Stiff should be playing Regular, and most playing Regular at 82 mph should be playing Senior. There is no performance penalty in a softer shaft that matches your load, and there is a real one in a shaft you cannot bend. Nobody has ever looked at a scorecard and seen which letter was printed on the butt section.