Method and system for obtaining equivalent simple pendulum length and moment of inertia for golf club optimal for golfer, selection method for golf club, as well as method for obtaining position and weight of weight suitable for each golfer

This method for obtaining an equivalent simple pendulum length and a moment of inertia for a golf club which is optimal for each golfer is provided with steps for: collecting data related to the characteristics of each golfer including physical characteristics of the golfers (first data) and data related to motion at swing time of each of the golfers (second data); and obtaining the equivalent simple pendulum length and the moment of inertia suitable for each of the golfers on the basis of the first data and the second data collected from each of the golfers, and predetermined rules constructed from the first data and the second data collected from a plurality of experts and selection results of optimal golf clubs selected by each of the plurality of experts.