Miami County area

Population and density of Miami County

The Census Bureau estimates that 112,634 people lived in Miami County on July 1, 2025. That ranks #576 of 3,222 county equivalents nationally and #25 of 88 in Ohio. Since the April 1, 2020 estimates base of 108,781, the population has grown by 3,853 (+3.5%), compared with +0.9% for Ohio as a whole.

With 406.6 square miles of land, that is 277 people per square mile (107 per km²), placing Miami County #539 nationally for density and #22 in Ohio. The median county equivalent has 47 people per square mile; the Ohio median is 120. Put another way, there are about 2.3 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 Miami County

14 incorporated places lie at least partly in Miami County. Together they are home to 76,329 people (67.8%); the other 36,305 (32.2%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Troy city, with 27,344 residents in the county. By land, Huber Heights city is the largest at 22.7 mi² across all its counties. Among places with at least 1,000 residents in 2020, West Milton village grew fastest since then (+3.8%).

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

Metropolitan area

Miami County is an outlying county of the Dayton-Kettering-Beavercreek, OH Metropolitan Statistical Area. Its 3 county equivalents have 826,554 residents on 1,281.6 square miles of land; Miami County accounts for 31.7% of the land and 13.6% of the residents. By combined land it ranks #243 of 393 metropolitan areas, and #77 by population. It belongs to the Dayton-Springfield-Kettering, OH Combined Statistical Area.

ZIP codes

18 ZIP Code Tabulation Areas have land in Miami County; 11 of them have most of their land inside the county, and the others mainly cover neighboring areas.

453044530845309453124531745318453224532645337453394534445356453594536145371453734538345424

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 Miami County

Miami County shares a land border with 5 county equivalents. It has more land than 1 of them. The largest neighbor is Darke County (598.1 mi²) and the smallest is Clark County (395.9 mi²). Together with its neighbors, Miami County forms a block of 2,698.6 mi² of land, of which it holds 15.1%.

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

Miami County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 2.5 times as much. Ohio’s county land could hold about 100 areas the size of Miami County.

Another way to picture it: the same land area would fill a square about 20.2 miles (32.5 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 Miami County?

Miami County has more land than 731 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 Miami County at #2,547 nationally by total area, 56 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 0.7%, compared with a national county-equivalent median of 1.2% — 0.4 percentage points lower. 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 Miami 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.