Flathead County, MT population age distribution
A complete breakdown of Flathead County's age demographics from 0 to 85 years, distributed across 18 age groups is listed in the table below.
Age Group | Population | % of Total Population |
---|---|---|
Under 5 years | 5,684 | 5.5% |
5 to 9 years | 6,041 | 5.84% |
10 to 14 years | 6,999 | 6.77% |
15 to 19 years | 5,952 | 5.76% |
20 to 24 years | 4,961 | 4.8% |
25 to 29 years | 6,077 | 5.88% |
30 to 34 years | 6,300 | 6.09% |
35 to 39 years | 6,558 | 6.34% |
40 to 44 years | 6,552 | 6.34% |
45 to 49 years | 6,281 | 6.07% |
50 to 54 years | 6,200 | 6% |
55 to 59 years | 6,585 | 6.37% |
60 to 64 years | 8,936 | 8.64% |
65 to 69 years | 7,375 | 7.13% |
70 to 74 years | 5,771 | 5.58% |
75 to 79 years | 3,578 | 3.46% |
80 to 84 years | 1,768 | 1.71% |
85 years and over | 1,782 | 1.72% |
TABLE OF CONTENTS
Flathead County, MT population by age group
Sources: U.S. Census Bureau, American Community Survey (ACS) 2021

The largest age group in Flathead County, MT was for the group of age 60-64 years with a population of 8,936 (8.64%), according to the 2021 American Community Survey.
At the same time, the smallest age group in Flathead County, MT was the 80-84 years with a population of 1,768 (1.71%).
Flathead County, MT population by age cohort
To better understand the age distribution of Flathead County, MT's population, we divided it into the following 3 cohorts:
- Children : Under the age of 18 years
- Adults (working population): Between the age of 18 and 64 years
- Seniors: 65 years and above

Here's the population for each of the three cohorts.
Age Group | Population | % of Total Population |
---|---|---|
Under 18 years | 22,673 | 21.93% |
18 to 64 years | 60,453 | 58.47% |
85 years and over | 20,274 | 19.61% |
Key stats for each age cohort as per our analysis of U.S. Census Bureau American Community Survey:
- Flathead County's population under 18 was 21.93%, compared to the 22.51% nationwide.
- Flathead County's working population (between 18 and 64) was 58.47%, compared to 61.45% nationwide.
- Flathead County's elderly or the senior population (over 65 age) was 19.61% as compared to 16.04% nationwide.
Flathead County, MT population pyramid
Population pyramid for Flathead County, MT is charted below using the estimates from U.S. Census Bureau's American Community Survey 5-Year estimates. A wide base suggests population increase, narrow base indicates declining birth rates.
Key stats from our analysis of the Flathead County's population pyramid:
- Youth dependency ratio, which is the number of children aged 0-14 per 100 persons aged 15-64, for Flathead County, MT, is 29.1.
- Old-age dependency ratio, which is the number of persons aged 65 or over per 100 persons aged 15-64, for Flathead County, MT, is 31.5.
- Total dependency ratio for Flathead County, MT is 60.6.
- Potential support ratio, which is the number of youth (working age population) per elderly, for Flathead County, MT is 3.2.

Here's the Flathead County, MT's male and female population across different age groups:
Age Group | Population(Male) | Population(Female) | Total Population |
---|---|---|---|
Under 5 years | 2,867 | 2,817 | 5,684 |
5 to 9 years | 3,510 | 2,531 | 6,041 |
10 to 14 years | 3,332 | 3,667 | 6,999 |
15 to 19 years | 3,109 | 2,843 | 5,952 |
20 to 24 years | 2,566 | 2,395 | 4,961 |
25 to 29 years | 2,963 | 3,114 | 6,077 |
30 to 34 years | 3,201 | 3,099 | 6,300 |
35 to 39 years | 3,610 | 2,948 | 6,558 |
40 to 44 years | 2,932 | 3,620 | 6,552 |
45 to 49 years | 3,202 | 3,079 | 6,281 |
50 to 54 years | 3,087 | 3,113 | 6,200 |
55 to 59 years | 3,275 | 3,310 | 6,585 |
60 to 64 years | 4,220 | 4,716 | 8,936 |
65 to 69 years | 3,483 | 3,892 | 7,375 |
70 to 74 years | 3,037 | 2,734 | 5,771 |
75 to 79 years | 1,785 | 1,793 | 3,578 |
80 to 84 years | 972 | 796 | 1,768 |
85 years and over | 645 | 1,137 | 1,782 |
Things to know
What is the population of Flathead County, MT under 18?
Flathead County's population under the age of 18 is 22,673, as per the latest U.S. Census Bureau's American Community Survey estimates. This population is 21.93% of the total resident population of Flathead County, MT.
What is the aging population in Flathead County, MT?
Flathead County's population aged 65 years and above was 20,274. As per the U.S. Census Bureau's American Community Survey, this population is 19.61% of the entire population.
References
- U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates