How many people live in Boulder County, CO?
Updated Apr. 6, 2026Refreshed annually
In 2024, there were about 330,300 people living in Boulder County, CO. That makes Boulder County the ninth-most populous county in Colorado. It is home to 5.5% of people living in the state.
330K
population of Boulder County, CO (2024)
5.5%
County share of the Colorado population (2024)
About 330,300 people lived in Boulder County, CO in 2024.
Population estimates, 2000–2024
What are Boulder County, CO’s age demographics?
About 57,900 Boulder County residents are aged 65 and older in 2024. That represents 17.5% of its population. For comparison, the age group represents 16.5% of Colorado’s population and 18% in the US overall.
Another 54,800 Boulder County residents, or 16.6% of the population, were children under 18. For comparison, the age group represents 20.5% of Colorado’s population and 21.6% in the US overall.
A higher share of Boulder County, CO's population is aged 18–24 than the US as a whole.
Population estimates by age group, (2024)
What are Boulder County, CO’s racial and ethnic demographics?
Non-Hispanic white residents make up 75.4% of the Boulder County, CO population, higher than the national share of 57.5%. Boulder County, CO also has a larger share of people identifying as non-Hispanic two or more races (2.5%) than the US overall (2.5%).
In contrast, Boulder County’s non-Hispanic Black or African American population accounts for 1.1%, below the 12.6% nationwide, and the Hispanic population makes up 15% of the county, compared with 20% nationally.
Racial and ethnic make up differ based on location. These figures reflect how people identified their race alone (not in combination with other races), and separate out Hispanic or Latino ethnicity, following Census reporting standards.
Boulder County, CO has a higher share of a non-Hispanic white population than Colorado as a whole.
Population estimates by race and ethnicity, (2024)
The largest city or town in Boulder County, CO is Boulder with about 106,800 residents in 2024.
Cities and towns in Boulder County, CO ranked by population
Population (2024), includes only portions within county
| City or town | Population | |
|---|---|---|
| 1. | Boulder | 106,803 |
| 2. | Longmont (pt.) | 98,503 |
| 3. | Lafayette | 30,587 |
| 4. | Louisville | 20,811 |
| 5. | Erie (pt.) | 14,889 |
| 6. | Superior (pt.) | 13,654 |
| 7. | Lyons | 2,155 |
| 8. | Nederland | 1,487 |
| 9. | Jamestown | 246 |
| 10. | Ward | 127 |
Keep exploring
Methodology
USAFacts standardizes data, in areas such as time and demographics, to make it easier to understand and compare.
The analysis was generated with the help of AI and reviewed by USAFacts for accuracy.
Page sources
USAFacts endeavors to share the most up-to-date information available. We sourced the data on this page directly from government agencies; however, the intervals at which agencies publish updated data vary.
