ZIP codes

ZIP codes in Boulder County, Colorado

Boulder County has 23 ZIP codes. 16 lie entirely inside it and 7 are shared with neighboring counties, so part of their land and their people are elsewhere. About 326,115 people live in the parts inside it (ACS 2020–2024).

By the All Map Tools Team

ZIP codes: 23; With 1% or more of their land inside
Entirely inside: 16; 99% or more of their land
Shared with other counties: 7; Most with Larimer County (3)
Most populated ZIP: 80501; 44,147 people · Longmont
Least populated ZIP: 80025; 138 people · Eldorado Springs; 2 more with nobody living there
Largest ZIP by land: 80540; 153 sq mi · Allenspark

Map of the ZIP codes in Boulder County

Entirely in the county (99% or more of its land)
Shared, mostly in this county
Shared, mostly in other counties
Neighboring counties

Open in the interactive tool

Each area is a ZIP code with its number where it fits. Hover over one to see its name.

All ZIP codes in Boulder County

23 ZIP codes in Boulder County, CO, by number
ZIP code	Main city	Population	Land in the county	Residents in the county
80020	Broomfield	54,201	25%	≈ 3,743
80025	Eldorado Springs	138	100%	138
80026	Lafayette	32,701	99.5%	≈ 32,701
80027	Louisville	34,127	100%	34,127
80301	Boulder	25,007	100%	25,007
80302	Lazy Acres	29,569	100%	29,569
80303	Boulder	24,996	100%	24,996
80304	Boulder	25,383	100%	25,383
80305	Boulder	16,291	100%	16,291
80310	Boulder	7,692	100%	7,692
80403	Coal Creek	20,732	5.5%	≈ 366
80455	Glendale	501	100%	501
80466	Eldora	3,599	100%	3,599
80471	—	0	100%	0
80481	Bark Ranch	484	100%	484
80501	Longmont	44,147	100%	44,147
80503	Longmont	35,846	98%	≈ 35,750
80504	Firestone	63,451	41%	≈ 31,014
80510	Allenspark	663	100%	663
80513	Berthoud	18,271	5.3%	≈ 270
80516	Erie	39,048	14%	≈ 6,874
80540	Allenspark	4,642	65%	≈ 2,800
80544	Niwot	0	100%	0

ZIP codes shared with other counties

These 7 ZIP codes have part of their land in another county. The first figure is the share of their land in Boulder County; then, where the rest lies.

80020 (Broomfield): 25% here; 60% in Broomfield County, 13% in Jefferson County, and 2.2% in Adams County.
80403 (Coal Creek): 5.5% here; 82% in Jefferson County and 12% in Gilpin County.
80503 (Longmont): 98% here; 2.1% in Larimer County.
80504 (Firestone): 41% here; 59% in Weld County.
80513 (Berthoud): 5.3% here; 64% in Larimer County and 31% in Weld County.
80516 (Erie): 14% here; 77% in Weld County and 9.2% in Broomfield County.
80540 (Allenspark): 65% here; 35% in Larimer County.

Cities and prefixes

By main city (the city, town or CDP each ZIP shares the most land with), the ones with the most are Boulder (5), Allenspark (2), Longmont (2), Bark Ranch (1), Berthoud (1), and Broomfield (1); 16 places in all.

They start with 4 different three-digit prefixes, one per USPS sorting center: 800, 803, 804, and 805.

Neighboring counties

Each one with its ZIP codes. Those without a page of their own open in the tool.

Tools for this county

ZIP codes by county or city The same ZIP codes on an interactive map, with the list as CSV or to copy County map with cities Its cities, towns and CDPs with their population ZIP codes in a radius The ZIP codes within 10 miles of its center, or any distance you like

Sources

U.S. Census Bureau, 2020 ZCTA to County, ZCTA to Place and ZCTA to Census Tract Relationship Files (and the 2022 County Subdivision to ZCTA file for Connecticut). Public domain.
U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates, table B01003 (population of each ZIP code, census tract and Connecticut town). Public domain.
U.S. Census Bureau, Vintage 2025 Population Estimates (county population) and 2025 Gazetteer Files (land area and interior point of each ZIP code). Public domain.
U.S. Census Bureau, Cartographic Boundary Files: ZCTAs 2020 and counties 2025, 1:500,000; county adjacency file 2025. Public domain.

How we count. ZIP codes here are the Census Bureau’s ZIP Code Tabulation Areas (ZCTAs), the areas it draws to match USPS ZIP codes; ZIPs with no area of their own (PO boxes, single buildings) aren’t included. A ZIP can cross county lines: “Land in the county” is the exact share of its land inside, from the Census relationship files. “Residents in the county” is the whole ZIP for those entirely inside; for shared ones it’s an estimate, spreading the people of each census tract over the land it shares with the ZIP. Population: ACS 2020–2024. Methodology.

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