Purpose: This cross-sectional study aimed to investigate the ability to adjust grip strength by comparing the characteristics of force generation and relaxation from childhood to adulthood. Method: This study included 225 participants aged 6, 11, 17, and 19-23 years (adults) who performed isometric hand-grip force as follows: maximum, half generation, and half relaxation. The force was recorded, and relative values and errors were calculated for half tasks. Results: The maximum task values increased with age, but there was no significant age difference between 17-year-olds and adults. The difference between sexes was significant; males were stronger than females in both 17-year-olds and adults. Both sexes in all age groups had greater errors in half relaxation than in half generation tasks. Females had negatively greater constant error than males in half tasks. The errors of 6-year-olds were greater than the other age groups in half tasks. Conclusion: There is a developmental trend for producing maximal strength that is similar across sexes until adolescence when males are stronger and females plateau. The ability of force relaxation was more difficult to accurately control than force generation for all age groups and was adult-like by middle childhood.