San Francisco County area

Population and density of San Francisco County

The Census Bureau estimates that 826,079 people lived in San Francisco County on July 1, 2025. That ranks #79 of 3,222 county equivalents nationally and #13 of 58 in California. Since the April 1, 2020 estimates base of 878,550, the population has declined by 52,471 (−6%), compared with −0.5% for California as a whole.

With 46.7 square miles of land, that is 17,695 people per square mile (6,832 per km²), placing San Francisco County #5 nationally for density and #1 in California. The median county equivalent has 47 people per square mile; the California median is 112. Put another way, there are about 0.036 acres of land per resident.

U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.

Cities and towns in San Francisco County

Every resident of San Francisco County lives within San Francisco city. The city and the county equivalent cover the same territory, 46.7 square miles of land in the 2026 place Gazetteer, so there are no separate towns or unincorporated areas to list.

Metropolitan area

San Francisco County is a central county of the San Francisco-Oakland-Fremont, CA Metropolitan Statistical Area, in the San Francisco-San Mateo-Redwood City, CA metropolitan division. Its 5 county equivalents have 4,630,041 residents on 2,469.8 square miles of land; San Francisco County accounts for 1.9% of the land and 17.8% of the residents. By combined land it ranks #133 of 393 metropolitan areas, and #13 by population. It belongs to the San Jose-San Francisco-Oakland, CA Combined Statistical Area.

ZIP codes

30 ZIP Code Tabulation Areas have land in San Francisco County; 28 of them have most of their land inside the county, and the others mainly cover neighboring areas.

941029410394104941059410794108941099411094111941129411494115941169411794118941219412294123941249412794129941309413194132941339413494158941889450194920

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering San Francisco County

San Francisco County shares a land border with 3 county equivalents. Each of them has more land than San Francisco County. The largest neighbor is Alameda County (737.5 mi²) and the smallest is San Mateo County (448.6 mi²). Together with its neighbors, San Francisco County forms a block of 1,752.9 mi² of land, of which it holds 2.7%.

How big is San Francisco County compared with U.S. states?

San Francisco County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 22 times as much. California’s county land could hold about 3,339 areas the size of San Francisco County.

Another way to picture it: the same land area would fill a square about 6.83 miles (11 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.

State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.

What stands out about San Francisco County?

San Francisco County has more land than 89 of the other 3,221 county equivalents in the dataset.

A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.

Does including water change its rank?

Using land plus water places San Francisco County at #2,979 nationally by total area, 154 places closer to the top than its land rank. The water assigned to this geography moves it ahead of some county equivalents with more land.

Its water share is 79.9%, compared with a national county-equivalent median of 1.2% — 78.7 percentage points higher. This describes the statistical geography’s land/water mix, not flood exposure or developable land.

Closest positions in the national land ranking

These entries sit immediately beside San Francisco County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.