County outline
Where Guernsey County is located
Area breakdown
Land accounts for 98.9% of Guernsey County’s measured area and water for 1.1%. Its combined area converts to 1,368.3 square kilometers or approximately 338,106 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 522.242 | 1,352.601 | 334,234.9 |
| Water | 6.049 | 15.667 | 3,871.4 |
| Total | 528.291 | 1,368.267 | 338,106.2 |
How Guernsey County compares
By original Census land area, Guernsey County ranks #22 of 88 in Ohio and #1999 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.198 times the Ohio county-equivalent median of 436 square miles. It accounts for 1.3% of the combined county land area in the state.
See the complete Ohio ranking · What counts as a county equivalent?
Population and density of Guernsey County
The Census Bureau estimates that 38,379 people lived in Guernsey County on July 1, 2025. That ranks #1,248 of 3,222 county equivalents nationally and #64 of 88 in Ohio. Since the April 1, 2020 estimates base of 38,439, the population has declined by 60 (−0.2%), compared with +0.9% for Ohio as a whole.
With 522.2 square miles of land, that is 73 people per square mile (28 per km²), placing Guernsey County #1,222 nationally for density and #69 in Ohio. The median county equivalent has 47 people per square mile; the Ohio median is 120. Put another way, there are about 8.7 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 38,426 | 38,298 | 38,056 | 38,132 | 38,329 | 38,379 |
| Change | — | −128 | −242 | +76 | +197 | +50 |
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 Guernsey County
9 incorporated places lie at least partly in Guernsey County. Together they are home to 14,481 people (37.7%); the other 23,898 (62.3%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Cambridge city, with 10,055 residents in the county.
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Cambridge cityCounty seat | 10,055 | −0.7% | 6.367 |
| Byesville village | 2,359 | −0.5% | 1.198 |
| Senecaville village | 407 | −0.7% | 0.475 |
| Pleasant City village | 396 | −0.8% | 0.176 |
| Quaker City village | 375 | −1.3% | 0.526 |
| Cumberland village | 314 | −0.6% | 0.486 |
| Lore City village | 280 | −1.1% | 0.328 |
| Old Washington village | 227 | −0.9% | 0.672 |
| Fairview villageAlso in 1 other county | 68 | 0% | 0.401 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Guernsey County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
Guernsey County is a central county of the Cambridge, OH Micropolitan Statistical Area. Guernsey County is the area’s only county equivalent, so the micro area has the same 522.2 square miles of land. By combined land it ranks #419 of 542 micropolitan areas, and #344 by population. It belongs to the Columbus-Marion-Zanesville, OH Combined Statistical Area.
ZIP codes
20 ZIP Code Tabulation Areas have land in Guernsey County; 12 of them have most of their land inside the county, and the others mainly cover neighboring areas.
4372243723437244372543732437334373643749437504375543762437684377243773437784378043832438374397343983
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 Guernsey County
Guernsey County shares a land border with 6 county equivalents. It has more land than 2 of them. The largest neighbor is Muskingum County (664.5 mi²) and the smallest is Noble County (398 mi²). Together with its neighbors, Guernsey County forms a block of 3,650.8 mi² of land, of which it holds 14.3%.
| Bordering county equivalent | Land mi² | Size vs. Guernsey | Compare |
|---|---|---|---|
| Muskingum County | 664.5 | 1.3× larger | Compare |
| Tuscarawas County | 567.6 | 1.1× larger | Compare |
| Coshocton County | 563.9 | 1.1× larger | Compare |
| Belmont County | 532.2 | about the same | Compare |
| Harrison County | 402.3 | 1.3× smaller | Compare |
| Noble County | 398 | 1.3× smaller | Compare |
How big is Guernsey County compared with U.S. states?
Guernsey 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 times as much. Ohio’s county land could hold about 78 areas the size of Guernsey County.
Another way to picture it: the same land area would fill a square about 22.9 miles (36.8 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 Guernsey County?
Guernsey County has more land than 1,223 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 Guernsey County at #2,076 nationally by total area, 77 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 1.1%, compared with a national county-equivalent median of 1.2%. The two percentages are within 0.1 percentage points of each other. 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 Guernsey County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #1998 | Niagara County, New York | 522.3 | Compare |
| #1999 | Guernsey County, Ohio | 522.2 | This county |
| #2000 | Hood River County, Oregon | 522.2 | 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 40.056665, -81.497875. 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: 1,352,599,516 m²; AWATER: 15,666,082 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 Guernsey County?
Guernsey County, Ohio has 522.2 square miles (1,352.6 km²) of land and 6.049 square miles of water, for a total area of 528.3 square miles. It ranks #1999 of 3,222 U.S. county equivalents by land area.
Is Guernsey County the largest county in Ohio?
No. Guernsey County ranks #22 of 88 in Ohio by land area. The largest is Ashtabula County, with 702.4 square miles of land.
What counties border Guernsey County?
Guernsey County shares a land border with Noble County, Muskingum County, Belmont County, Tuscarawas County, Coshocton County, and Harrison County.
What is the population of Guernsey County?
The Census Bureau estimates Guernsey County had 38,379 residents on July 1, 2025, ranking #1,248 of 3,222 county equivalents. That is 73 people per square mile of land.
What is the county seat of Guernsey County?
The county seat of Guernsey County is Cambridge.
What cities and towns are in Guernsey County?
Guernsey County has 9 incorporated places. The most populous five are Cambridge city, Byesville village, Senecaville village, Pleasant City village, and Quaker City village; 23,898 residents live outside any incorporated place.
Is Guernsey County part of a metropolitan area?
Yes. It is a central county of the Cambridge, OH Micropolitan Statistical Area.
How many ZIP codes are in Guernsey County?
20 ZIP Code Tabulation Areas have land in Guernsey County, and 12 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Guernsey County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 2 times as much land.
How many acres of land are in Guernsey County?
The land measurement converts to approximately 334,235 acres. Including water, total area is approximately 338,106 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.