Suffolk County area

Population and density of Suffolk County

The Census Bureau estimates that 1,546,090 people lived in Suffolk County on July 1, 2025. That ranks #27 of 3,222 county equivalents nationally and #4 of 62 in New York. Since the April 1, 2020 estimates base of 1,525,920, the population has grown by 20,170 (+1.3%), compared with −1% for New York as a whole.

With 910.9 square miles of land, that is 1,697 people per square mile (655 per km²), placing Suffolk County #96 nationally for density and #9 in New York. The median county equivalent has 47 people per square mile; the New York median is 112. Put another way, there are about 0.377 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 Suffolk County

Suffolk County is divided into 12 cities and towns. In New York, county subdivisions are local governments, and together they cover all of the county’s land and residents.

The most populous is Brookhaven town, with 496,410 residents (32.1% of the county), and it is also the largest by land at 259.6 mi². The county seat, Riverhead town, has 36,394 residents. Among those with at least 1,000 residents in 2020, Southampton town grew fastest since then (+3.7%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Suffolk County. Land: 2026 Census Gazetteer. How communities are listed.

Metropolitan area

Suffolk County is a central county of the New York-Newark-Jersey City, NY-NJ Metropolitan Statistical Area, in the Nassau County-Suffolk County, NY metropolitan division. Its 22 county equivalents have 20,112,448 residents on 6,139.7 square miles of land; Suffolk County accounts for 14.8% of the land and 7.7% of the residents. By combined land it ranks #34 of 393 metropolitan areas, and #1 by population. It belongs to the New York-Newark, NY-NJ-CT-PA Combined Statistical Area.

ZIP codes

109 ZIP Code Tabulation Areas have land in Suffolk County; 108 of them have most of their land inside the county, and the others mainly cover neighboring areas.

06390117011170211703117041170511706117131171511716117171171811719117201172111722117241172511726117271172911730117311173311735117381173911740117411174211743117461174711749117511175211754117551175711758117631176411766117671176811769117701177211776117771177811779117801178211784117861178711788117891179011792117941179511796117981190111930119311193211933119341193511937119391194011941119421194411946119471194811949119501195111952119531195411955119561195711958119591196011961119621196311964119651196711968119701197111972119731197511976119771197811980

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 Suffolk County

Suffolk County shares a land border with 1 county equivalent. It has 3.2 times the land area of Nassau County.

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

Suffolk County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.1 times as much. New York’s county land could hold about 52 areas the size of Suffolk County.

Another way to picture it: the same land area would fill a square about 30.2 miles (48.6 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 Suffolk County?

Suffolk County has more land than 2,401 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 Suffolk County at #254 nationally by total area, 567 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 61.6%, compared with a national county-equivalent median of 1.2% — 60.4 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 Suffolk 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.