Boulder, CO population age distribution
A complete breakdown of Boulder'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 | 2,838 | 2.7% |
5 to 9 years | 3,892 | 3.71% |
10 to 14 years | 3,793 | 3.61% |
15 to 19 years | 12,481 | 11.89% |
20 to 24 years | 21,574 | 20.56% |
25 to 29 years | 10,349 | 9.86% |
30 to 34 years | 6,789 | 6.47% |
35 to 39 years | 5,533 | 5.27% |
40 to 44 years | 5,297 | 5.05% |
45 to 49 years | 5,486 | 5.23% |
50 to 54 years | 5,343 | 5.09% |
55 to 59 years | 4,738 | 4.52% |
60 to 64 years | 4,422 | 4.21% |
65 to 69 years | 3,560 | 3.39% |
70 to 74 years | 3,751 | 3.57% |
75 to 79 years | 2,025 | 1.93% |
80 to 84 years | 1,181 | 1.13% |
85 years and over | 1,878 | 1.79% |
TABLE OF CONTENTS
Boulder, CO population by age group
Sources: U.S. Census Bureau, American Community Survey (ACS) 2021

The largest age group in Boulder, CO was for the group of age 20-24 years with a population of 21,574 (20.56%), according to the 2021 American Community Survey.
At the same time, the smallest age group in Boulder, CO was the 80-84 years with a population of 1,181 (1.13%).
Boulder, CO population by age cohort
To better understand the age distribution of Boulder, CO'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 | 13,130 | 12.51% |
18 to 64 years | 79,405 | 75.67% |
85 years and over | 12,395 | 11.81% |
Key stats for each age cohort as per our analysis of U.S. Census Bureau American Community Survey:
- Boulder's population under 18 was 12.51%, compared to the 22.51% nationwide.
- Boulder's working population (between 18 and 64) was 75.67%, compared to 61.45% nationwide.
- Boulder's elderly or the senior population (over 65 age) was 11.81% as compared to 16.04% nationwide.
Boulder, CO population pyramid
Population pyramid for Boulder, CO 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 Boulder's population pyramid:
- Youth dependency ratio, which is the number of children aged 0-14 per 100 persons aged 15-64, for Boulder, CO, is 12.8.
- Old-age dependency ratio, which is the number of persons aged 65 or over per 100 persons aged 15-64, for Boulder, CO, is 15.1.
- Total dependency ratio for Boulder, CO is 27.9.
- Potential support ratio, which is the number of youth (working age population) per elderly, for Boulder, CO is 6.6.

Here's the Boulder, CO's male and female population across different age groups:
Age Group | Population(Male) | Population(Female) | Total Population |
---|---|---|---|
Under 5 years | 1,488 | 1,350 | 2,838 |
5 to 9 years | 2,019 | 1,873 | 3,892 |
10 to 14 years | 1,638 | 2,155 | 3,793 |
15 to 19 years | 6,229 | 6,252 | 12,481 |
20 to 24 years | 11,543 | 10,031 | 21,574 |
25 to 29 years | 5,805 | 4,544 | 10,349 |
30 to 34 years | 3,901 | 2,888 | 6,789 |
35 to 39 years | 2,818 | 2,715 | 5,533 |
40 to 44 years | 2,634 | 2,663 | 5,297 |
45 to 49 years | 2,994 | 2,492 | 5,486 |
50 to 54 years | 2,603 | 2,740 | 5,343 |
55 to 59 years | 2,442 | 2,296 | 4,738 |
60 to 64 years | 2,268 | 2,154 | 4,422 |
65 to 69 years | 1,757 | 1,803 | 3,560 |
70 to 74 years | 1,665 | 2,086 | 3,751 |
75 to 79 years | 933 | 1,092 | 2,025 |
80 to 84 years | 449 | 732 | 1,181 |
85 years and over | 846 | 1,032 | 1,878 |
Things to know
What is the population of Boulder, CO under 18?
Boulder's population under the age of 18 is 13,130, as per the latest U.S. Census Bureau's American Community Survey estimates. This population is 12.51% of the total resident population of Boulder, CO.
What is the aging population in Boulder, CO?
Boulder's population aged 65 years and above was 12,395. As per the U.S. Census Bureau's American Community Survey, this population is 11.81% of the entire population.
References
- U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates