Swingweight (SW, swing weight, swinging weight) is one of attempts to quantify the heft or headweight feel of a golf club. It specifies how heavy the club feels to a golfer swinging it.
In accordance with the principles of physics, club sets should be matched basing on moment of inertia (MOI) of the clubs about their butts, but in the past something was needed and the value of swingweight was easy to estimate. It is not a bad match at all and it is still traditionally used as the simplest method of matching club set.
In fact, there was no such thing as “swingweight” in the physics of a swing. It is an arbitrary expression of the weight distribution of a golf club. It is measured as the amount of torque the weight of the club exerted about a pivoting fulcrum point.
There are two different Swingweight scales: “Lorythmic” (the most popular nowadays) and “Official” (used in vintage scales).
Lorythmic (Lorythm) scale uses the fulcrum point at 14” from the butt. Value is expressed in a letter number designation. The lower the letter and number, the less the headweight will be noticed by the golfer when the club is swung. The letters used are A, B, C, D, E, F and G, and the numerals 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. A0 is the lightest measurement, progressing up to the heaviest, G9. The gap between adjacent combinations of letter and number is known as a “swingweight point”. The manufacturers’ standard for men’s clubs is D0 to D2, and for women’s clubs, C5 to C7.
Official scale is based on the fulcrum point at 12” from the butt. Swingweight is expressed in inch-ounces. Sometimes vintage “Official” scales are scaled in other units, so dedicated conversion charts are needed to use them. The manufacturers’ standard for men’s clubs is 240 to 250, and for women’s clubs, 230 to 240 inch-ounces. In this scale the gap of 2 inch-ounces is equivalent of one “swingweight point”.
Three swingweight points of difference is quite distinct and most golfers can feel the it. Some golfers can feel a difference of two points, but the difference in feel is subtle. Very few golfers can feel a difference of one swingweight point.
update: August 2016