Cobb County area

Population and density of Cobb County

The Census Bureau estimates that 793,345 people lived in Cobb County on July 1, 2025. That ranks #84 of 3,222 county equivalents nationally and #3 of 159 in Georgia. Since the April 1, 2020 estimates base of 766,088, the population has grown by 27,257 (+3.6%), compared with +5.5% for Georgia as a whole.

With 339.7 square miles of land, that is 2,335 people per square mile (902 per km²), placing Cobb County #68 nationally for density and #3 in Georgia. The median county equivalent has 47 people per square mile; the Georgia median is 69. Put another way, there are about 0.274 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 Cobb County

8 incorporated places lie at least partly in Cobb County. Together they are home to 290,009 people (36.6%); the other 503,336 (63.4%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Mableton city, with 78,820 residents in the county. The county seat, Marietta city, has 63,574 residents. By land, Roswell city is the largest at 40.7 mi² across all its counties. Among places with at least 1,000 residents in 2020, Powder Springs city grew fastest since then (+24.2%).

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

Metropolitan area

Cobb County is a central county of the Atlanta-Sandy Springs-Roswell, GA Metropolitan Statistical Area, in the Marietta, GA metropolitan division. Its 29 county equivalents have 6,482,182 residents on 8,784.1 square miles of land; Cobb County accounts for 3.9% of the land and 12.2% of the residents. By combined land it ranks #10 of 393 metropolitan areas, and #6 by population. It belongs to the Atlanta--Athens-Clarke County--Sandy Springs, GA-AL Combined Statistical Area.

ZIP codes

25 ZIP Code Tabulation Areas have land in Cobb County; 19 of them have most of their land inside the county, and the others mainly cover neighboring areas.

30008300603006230064300663006730068300753008030082300903010130102301063011130122301263012730141301443015230157301683018830339

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 Cobb County

Cobb County shares a land border with 5 county equivalents. It has more land than 2 of them. The largest neighbor is Fulton County (526.9 mi²) and the smallest is Douglas County (200.1 mi²). Together with its neighbors, Cobb County forms a block of 2,259 mi² of land, of which it holds 15%.

How big is Cobb County compared with U.S. states?

Cobb County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 3 times as much. Georgia’s county land could hold about 170 areas the size of Cobb County.

Another way to picture it: the same land area would fill a square about 18.4 miles (29.7 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 Cobb County?

Cobb County has more land than 509 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 Cobb County at #2,750 nationally by total area, 37 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.

Its water share is 1.3%, compared with a national county-equivalent median of 1.2% — 0.2 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 Cobb 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.