What is the largest city in Boulder County, CO?

Boulder is the largest city or town in Boulder County, with about 106,433 residents.

How many ZIP codes are in Boulder County?

Boulder County includes 18 ZIP Code Tabulation Areas, including 80025, 80026, 80027, 80301, 80302.

What is the population of Boulder County, CO?

About 328,961 people live in Boulder County, based on American Community Survey 5-year estimates.

What counties border Boulder County?

Boulder County borders Jefferson County, Larimer County, Weld County, Broomfield County, Grand County, Gilpin County.

Boulder County, CO: Cities, ZIP Codes & Local Data

Population

328,961

Land area

726sq mi

People per sq mi

453

ZIP codes

18

Boulder County at a glance

Boulder County is about 8 times as dense as Colorado as a whole.
By population, it ranks 9th among 64 counties in Colorado.
The median household income is $103,994, 9% above the Colorado median of $95,470.
A typical owner-occupied home is valued at $756,300 (40% above Colorado) and median rent is $1,966 a month.
Its largest cities are Boulder (106,433), Longmont (99,406) and Lafayette (30,602).

Local data for Boulder County, CO

Counts from official public data

Housing and community stats

Boulder County, CO, American Community Survey 2020-2024

Full profile

Median household income

$103,994

Poverty rate

11.2%

Median home value

$756,300

Prices -0.1% in a year

Median rent

$1,966/mo

Homeownership

62.0%

Bachelor's or higher

64.2%

Median age

37.7

Average commute

22.3 min

Largest reported origins and ancestries: German Americans (59,472), Irish Americans (41,601), Mexican Americans (32,550).

Home values and rents Income, education and commute

Economy and federal money

Jobs, income, federal spending and pandemic loans

Details

Unemployment rate

4.6%

Aug 2026, +0.7 pts in a year

Average annual pay

$101,259

191,487 jobs, 2025

Income per person

$104,808

BEA, 2024

Federal spending

$3.19B

FY 2026, $9,642 per person

PPP loans

$1.21B

13,701 loans, 128,090 jobs reported

Campaign donations

$8.26M

Itemized, 2026 cycle

Economy Federal spending PPP loans

How people get to work

Boulder County, CO, workers 16 and older. American Community Survey 5-year estimates

Drove alone52.8%
Carpooled5.3%
Public transit2.6%
Walked4.0%
Bicycle3.1%
Taxi, ride-hailing, motorcycle or other0.9%
Worked from home31.2%

Average one-way commute: 22.3 minutes for people who do not work from home.

Environment and hazard risk

Boulder County, CO, from FEMA, NOAA and EPA

Full report

Natural hazard risk

Relatively Moderate

Top: lightning

Storm events since 1996

1,987

Most often winter storm

Flood insurance policies

2,543

2.3% of homes, county

July high / Jan low

88° / 22°F

21.2 inches of rain a year

Hazards, floods and storm history Check a flood zone 66 historic places

Health statistics

Share of adults in Boulder County, CO, CDC PLACES estimates

All 40 measures

Obesity

16.7%

U.S. 33.3% -16.6 pts

Diabetes

7.1%

U.S. 12.1% -5.0 pts

Smoking

8.8%

U.S. 12.8% -4.0 pts

Uninsured (18-64)

7.8%

U.S. 11.1% -3.3 pts

Cities, towns and ZIP codes in Boulder County

Population shown

Frequently asked questions

What is the largest city in Boulder County, CO?: Boulder is the largest city or town in Boulder County, with about 106,433 residents.
How many ZIP codes are in Boulder County?: Boulder County includes 18 ZIP Code Tabulation Areas, including 80025, 80026, 80027, 80301, 80302.
What is the population of Boulder County, CO?: About 328,961 people live in Boulder County, based on American Community Survey 5-year estimates.
What counties border Boulder County?: Boulder County borders Jefferson County, Larimer County, Weld County, Broomfield County, Grand County, Gilpin County.