A tool to evaluate the subjective wearing comfort of baseball caps from the objective measurement of pressure was developed. Comfortable fittability index(CFI) and holding power(HP) were defined to represent the subjective wearing comfort of caps. In order to define the CFI, average pressure and pressure distribution of cap pressure were obtained and subjective sensations were evaluated by wearing test. Two sets of caps were evaluated, one set made of elastic fabric(F-caps) and the other set made of non-elastic fabric(S-caps). F-caps exerted lower average pressure and smaller pressure distribution. In wearing test results, F-caps were comfortable within the wide rage of the cap size. Form the results obtained, we tried to find the statistical relationship between the objective pressure and HP or CFI values. HP values increased with the increase of average pressure and also with pressure distribution, regardless of the textile properties. We analyzed the regression equation to estimate HP and pressure sensation utilizing average pressure and pressure distribution, and constructed the regression equation to estimated CFI using the calculated pressure sensation. We programmed such estimated data in an algorithm and connected the measuring equipment of a cap pressure. Finally, a tool was developed to measure comfort and HP of a base ball cap from measuring the pressure inside caps.