Big Arm is a CDP located in Lake County, Montana. Big Arm has a 2026 population of 134. Big Arm is currently declining at a rate of -2.19% annually and its population has decreased by 0% since the most recent census, which recorded a population of 0 in 2020.
The median age in Big Arm is 29.9 years: 40.7 years for males, and 29.7 years for females. For every 100 females there are 120.9 males.
Data after 2023 is projected based on recent change
Overall: 29.9 years
Female: 29.7 years
Male: 40.7 years
There are 123 adults, (23 of whom are seniors) in Big Arm.
Female: 86 (45.3%)
Male: 104 (54.7%)
The racial composition of Big Arm includes 47.37% Native American, 31.05% White, 21.58% Native Hawaiian or Pacific Islander, and smaller percentages for and multiracial populations.
| Race | Population ↓ | Percentage (of total) |
|---|---|---|
| Native American | 90 | 47.37% |
| White | 59 | 31.05% |
| Native Hawaiian or Pacific Islander | 41 | 21.58% |