Body mass, along with standard measurements, is much more frequently measured than total length or wingspan in different populations. Museum specimens from the western United States averaged in 48 males and in 20 females, while those sourced from the eastern United States averaged in 16 males and in 31 females. Average weight of 104 male migrating hawks in Cedar Grove, Wisconsin was (with adults averaging 4% heavier than juveniles), whilst the average of 115 females migrants was (with adult averaging about 5.5% heavier than juveniles). A different sample of Wisconsin Cooper's hawks reportedly averaged in males (sample size 60) and in females (sample size 57). At Cape May Point, New Jersey, weights were similar as in Wisconsin (although only hatching-year juveniles were apparently weighed), with averages of in two samples of males and in the two samples for females. Migrant hawks in the Goshute Mountains of Nevada were significantly lighter than the eastern ones at in 183 first year males and in 177 older males and in 310 first year females and in 416 older females. Weights were similar to the Goshutes in the Marin Headlands, California where 50 males (all first-years) averaged and 117 first-year females averaged . Averaged between early and late summer, the average mass of males in Oregon was and that of females was reported at . The average weights of Cooper's hawks from Oregon was about 19.4% lower in males and 14.5% lower in females than those from Wisconsin but the Oregon hawks evidenced less seasonal variation in weight. In British Columbia, males averaged and females averaged while in western and eastern North Dakota, males averaged and females averaged . In northern Florida, males averaged and females averaged . In general, males may weigh anywhere from and females anywhere from , the lightest hawks generally being juveniles recorded from the Goshutes of Nevada, the heaviest known being adults from Wisconsin.