County outline
Where Nantucket County is located
Area breakdown
Land accounts for 15.2% of Nantucket County’s measured area and water for 84.8%. Its combined area converts to 786.5 square kilometers or approximately 194,339 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 46.192 | 119.637 | 29,562.9 |
| Water | 257.463 | 666.826 | 164,776.3 |
| Total | 303.655 | 786.463 | 194,339.2 |
How Nantucket County compares
By original Census land area, Nantucket County ranks #14 of 14 in Massachusetts and #3138 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 0.086 times the Massachusetts county-equivalent median of 540.2 square miles. It accounts for 0.6% of the combined county land area in the state.
See the complete Massachusetts ranking · What counts as a county equivalent?
Population and density of Nantucket County
The Census Bureau estimates that 14,758 people lived in Nantucket County on July 1, 2025. That ranks #2,177 of 3,222 county equivalents nationally and #14 of 14 in Massachusetts. Since the April 1, 2020 estimates base of 14,251, the population has grown by 507 (+3.6%), compared with +1.7% for Massachusetts as a whole.
With 46.2 square miles of land, that is 319 people per square mile (123 per km²), placing Nantucket County #486 nationally for density and #10 in Massachusetts. The median county equivalent has 47 people per square mile; the Massachusetts median is 673. Put another way, there are about 2 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 14,240 | 14,518 | 14,502 | 14,562 | 14,713 | 14,758 |
| Change | — | +278 | −16 | +60 | +151 | +45 |
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 Nantucket County
Nantucket County is divided into 1 county subdivision. In Massachusetts, county subdivisions are local governments, and together they cover all of the county’s land and residents.
The most populous is Nantucket town, with 14,758 residents (100% of the county), and it is also the largest by land at 46.2 mi².
Metropolitan area
Nantucket County is a central county of the Nantucket, MA Micropolitan Statistical Area. Nantucket County is the area’s only county equivalent, so the micro area has the same 46.2 square miles of land. By combined land it ranks #542 of 542 micropolitan areas, and #537 by population.
ZIP codes
3 ZIP Code Tabulation Areas have land in Nantucket County, and each lies mostly inside the county.
025540256402584
ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Post-office-box and single-address ZIP Codes have no tabulation area.
Counties bordering Nantucket County
Nantucket County has no land border with another county equivalent in the Census cartographic boundaries: open water separates it from every other county equivalent. Its nearest entries in the national land ranking are listed below, and the Massachusetts directory lists every county equivalent in the state.
How big is Nantucket County compared with U.S. states?
Nantucket 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. Massachusetts’s county land could hold about 169 areas the size of Nantucket County.
Another way to picture it: the same land area would fill a square about 6.80 miles (10.9 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 Nantucket County?
Nantucket County has more land than 84 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 Nantucket County at #2,841 nationally by total area, 297 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 84.8%, compared with a national county-equivalent median of 1.2% — 83.6 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 Nantucket County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #3137 | Hudson County, New Jersey | 46.2 | Compare |
| #3138 | Nantucket County, Massachusetts | 46.2 | This county |
| #3139 | Vega Baja Municipio, Puerto Rico | 45.9 | Compare |
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.
Representative coordinates
The Census internal point is 41.293102, -70.101500. It represents a location inside the geography; it is not necessarily the centroid or the address of a courthouse.
Source and precision
U.S. Census Bureau, 2026 Gazetteer Files, Counties. Original ALAND: 119,637,312 m²; AWATER: 666,826,412 m². Rankings use ALAND; exact ties use ascending GEOID. Tables preserve Census-published square miles to three decimals, with conversions based on those values.
Common questions
How big is Nantucket County?
Nantucket County, Massachusetts has 46.2 square miles (119.6 km²) of land and 257.5 square miles of water, for a total area of 303.7 square miles. It ranks #3138 of 3,222 U.S. county equivalents by land area.
Is Nantucket County the largest county in Massachusetts?
No. Nantucket County ranks #14 of 14 in Massachusetts by land area. The largest is Worcester County, with 1,510.7 square miles of land.
What counties border Nantucket County?
None. Open water separates Nantucket County from every other county equivalent in the Census cartographic boundaries.
What is the population of Nantucket County?
The Census Bureau estimates Nantucket County had 14,758 residents on July 1, 2025, ranking #2,177 of 3,222 county equivalents. That is 319 people per square mile of land.
What is the county seat of Nantucket County?
The county seat of Nantucket County is Nantucket.
Is Nantucket County part of a metropolitan area?
Yes. It is a central county of the Nantucket, MA Micropolitan Statistical Area.
How many ZIP codes are in Nantucket County?
3 ZIP Code Tabulation Areas have land in Nantucket County, and 3 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Nantucket County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 22.4 times as much land.
How many acres of land are in Nantucket County?
The land measurement converts to approximately 29,563 acres. Including water, total area is approximately 194,339 acres. One square mile equals 640 acres.
Why might another source show a different area?
Check whether it reports land or total area, its Census vintage, and its rounding. Our guide explains how to reconcile county area figures.
Can this establish a property boundary?
No. Statistical measurements and generalized maps do not establish property lines. Consult the relevant local surveying or land-records authority.