Hamilton County area

Population and density of Hamilton County

The Census Bureau estimates that 387,036 people lived in Hamilton County on July 1, 2025. That ranks #199 of 3,222 county equivalents nationally and #4 of 92 in Indiana. Since the April 1, 2020 estimates base of 347,490, the population has grown by 39,546 (+11.4%), compared with +2.8% for Indiana as a whole.

With 394.4 square miles of land, that is 981 people per square mile (379 per km²), placing Hamilton County #192 nationally for density and #3 in Indiana. The median county equivalent has 47 people per square mile; the Indiana median is 88. Put another way, there are about 0.652 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 Hamilton County

8 incorporated places lie at least partly in Hamilton County. Together they are home to 366,331 people (94.7%); the other 20,705 (5.3%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Carmel city, with 105,634 residents in the county. The county seat, Noblesville city, has 76,111 residents. Among places with at least 1,000 residents in 2020, Westfield city grew fastest since then (+42.7%).

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

Metropolitan area

Hamilton County is a central county of the Indianapolis-Carmel-Greenwood, IN Metropolitan Statistical Area. Its 11 county equivalents have 2,205,695 residents on 4,086 square miles of land; Hamilton County accounts for 9.7% of the land and 17.5% of the residents. By combined land it ranks #71 of 393 metropolitan areas, and #33 by population. It belongs to the Indianapolis-Carmel-Muncie, IN Combined Statistical Area.

ZIP codes

23 ZIP Code Tabulation Areas have land in Hamilton County; 13 of them have most of their land inside the county, and the others mainly cover neighboring areas.

4603046031460324603346034460374603846040460504605546060460624606946074460774623646240462504625646260462684628046290

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 Hamilton County

Hamilton County shares a land border with 6 county equivalents. It has more land than 2 of them. The largest neighbor is Madison County (451.9 mi²) and the smallest is Tipton County (260.5 mi²). Together with its neighbors, Hamilton County forms a block of 2,636.7 mi² of land, of which it holds 15%.

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

Hamilton County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 2.6 times as much. Indiana’s county land could hold about 91 areas the size of Hamilton County.

Another way to picture it: the same land area would fill a square about 19.9 miles (32 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 Hamilton County?

Hamilton County has more land than 669 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 Hamilton County at #2,592 nationally by total area, 39 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 2%, compared with a national county-equivalent median of 1.2% — 0.8 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 Hamilton 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.