San Diego County area

Population and density of San Diego County

The Census Bureau estimates that 3,282,248 people lived in San Diego County on July 1, 2025. That ranks #5 of 3,222 county equivalents nationally and #2 of 58 in California. Since the April 1, 2020 estimates base of 3,298,648, the population has declined by 16,400 (−0.5%), compared with −0.5% for California as a whole.

With 4,210.9 square miles of land, that is 779 people per square mile (301 per km²), placing San Diego County #233 nationally for density and #9 in California. The median county equivalent has 47 people per square mile; the California median is 112. Put another way, there are about 0.821 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 Diego County

18 incorporated places lie at least partly in San Diego County. Together they are home to 2,781,887 people (84.8%); the other 500,361 (15.2%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is San Diego city, with 1,406,106 residents in the county. Among places with at least 1,000 residents in 2020, Coronado city grew fastest since then (+4.4%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside San Diego County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.

Metropolitan area

San Diego County is a central county of the San Diego-Chula Vista-Carlsbad, CA Metropolitan Statistical Area. San Diego County is the area’s only county equivalent, so the metro area has the same 4,210.9 square miles of land. By combined land it ranks #68 of 393 metropolitan areas, and #18 by population.

ZIP codes

116 ZIP Code Tabulation Areas have land in San Diego County; 115 of them have most of their land inside the county, and the others mainly cover neighboring areas.

9190191902919059190691910919119191391914919159191691917919319193291934919359194191942919459194891950919629196391977919789198092003920049200792008920099201092011920149201992020920219202492025920269202792028920299203692037920409205492055920569205792058920599206092061920649206592066920679206992070920719207592078920819208292083920849208692091920929209392096921019210292103921049210592106921079210892109921109211192113921149211592116921179211892119921209212192122921239212492126921279212892129921309213192132921349213592136921399214092145921479215492155921619217392179921829256292672

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 Diego County

San Diego County shares a land border with 3 county equivalents. It has more land than 2 of them. The largest neighbor is Riverside County (7,209 mi²) and the smallest is Orange County (793.2 mi²). Together with its neighbors, San Diego County forms a block of 16,388.6 mi² of land, of which it holds 25.7%.

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

San Diego County has more land than 2 of the 50 states. It is about 2.2 times the land area of Delaware (1,948.6 mi²), while Connecticut, the next larger state, has 1.2 times as much land (4,842.5 mi²). California’s county land could hold about 37 areas the size of San Diego County.

Another way to picture it: the same land area would fill a square about 64.9 miles (104.4 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 Diego County?

San Diego County has more land than 3,111 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 Diego County at #108 nationally by total area, 3 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 7%, compared with a national county-equivalent median of 1.2% — 5.8 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 Diego 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.