County outline
Where St. Johns County is located
Area breakdown
Land accounts for 73.1% of St. Johns County’s measured area and water for 26.9%. Its combined area converts to 2,127.8 square kilometers or approximately 525,780 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 600.66 | 1,555.702 | 384,422.4 |
| Water | 220.872 | 572.056 | 141,358.1 |
| Total | 821.532 | 2,127.758 | 525,780.5 |
How St. Johns County compares
By original Census land area, St. Johns County ranks #44 of 67 in Florida and #1623 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 0.862 times the Florida county-equivalent median of 696.5 square miles. It accounts for 1.1% of the combined county land area in the state.
See the complete Florida ranking · What counts as a county equivalent?
Population and density of St. Johns County
The Census Bureau estimates that 346,328 people lived in St. Johns County on July 1, 2025. That ranks #218 of 3,222 county equivalents nationally and #21 of 67 in Florida. Since the April 1, 2020 estimates base of 273,426, the population has grown by 72,902 (+26.7%), compared with +8.9% for Florida as a whole.
With 600.7 square miles of land, that is 577 people per square mile (223 per km²), placing St. Johns County #305 nationally for density and #15 in Florida. The median county equivalent has 47 people per square mile; the Florida median is 209. Put another way, there are about 1.1 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 277,119 | 293,352 | 307,645 | 320,954 | 333,334 | 346,328 |
| Change | — | +16,233 | +14,293 | +13,309 | +12,380 | +12,994 |
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 St. Johns County
3 incorporated places lie at least partly in St. Johns County. Together they are home to 22,952 people (6.6%); the other 323,376 (93.4%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is St. Augustine city, with 16,141 residents in the county. Among places with at least 1,000 residents in 2020, St. Augustine city grew fastest since then (+12.7%).
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| St. Augustine cityCounty seat | 16,141 | +12.7% | 9.522 |
| St. Augustine Beach city | 6,810 | +0.1% | 2.132 |
| Marineland townAlso in 1 other county | 1 | 0% | 0.39 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside St. Johns County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
St. Johns County is a central county of the Jacksonville, FL Metropolitan Statistical Area. Its 5 county equivalents have 1,785,500 residents on 3,201.9 square miles of land; St. Johns County accounts for 18.8% of the land and 19.4% of the residents. By combined land it ranks #95 of 393 metropolitan areas, and #39 by population. It belongs to the Jacksonville-Kingsland-Palatka, FL-GA Combined Statistical Area.
| County equivalent | Population 2025 | Land mi² |
|---|---|---|
| Duval County | 1,062,963 | 762.7 |
| St. Johns County | 346,328 | 600.7 |
| Clay County | 239,593 | 604.6 |
| Nassau County | 106,879 | 648.7 |
| Baker County | 29,737 | 585.2 |
ZIP codes
12 ZIP Code Tabulation Areas have land in St. Johns County; 10 of them have most of their land inside the county, and the others mainly cover neighboring areas.
320333208032081320823208432086320923209532131321453222432259
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 St. Johns County
St. Johns County shares a land border with 4 county equivalents. It has more land than 1 of them. The largest neighbor is Duval County (762.7 mi²) and the smallest is Flagler County (486.2 mi²). Together with its neighbors, St. Johns County forms a block of 3,182.5 mi² of land, of which it holds 18.9%.
| Bordering county equivalent | Land mi² | Size vs. St. Johns | Compare |
|---|---|---|---|
| Duval County | 762.7 | 1.3× larger | Compare |
| Putnam County | 728.4 | 1.2× larger | Compare |
| Clay County | 604.6 | about the same | Compare |
| Flagler County | 486.2 | 1.2× smaller | Compare |
How big is St. Johns County compared with U.S. states?
St. Johns County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.7 times as much. Florida’s county land could hold about 89 areas the size of St. Johns County.
Another way to picture it: the same land area would fill a square about 24.5 miles (39.4 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 St. Johns County?
St. Johns County has more land than 1,599 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 St. Johns County at #1,130 nationally by total area, 493 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 26.9%, compared with a national county-equivalent median of 1.2% — 25.7 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 St. Johns County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #1622 | Honolulu County, Hawaii | 600.8 | Compare |
| #1623 | St. Johns County, Florida | 600.7 | This county |
| #1624 | Pike County, Arkansas | 600.3 | 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 29.881393, -81.388281. 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: 1,555,701,129 m²; AWATER: 572,055,461 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 St. Johns County?
St. Johns County, Florida has 600.7 square miles (1,555.7 km²) of land and 220.9 square miles of water, for a total area of 821.5 square miles. It ranks #1623 of 3,222 U.S. county equivalents by land area.
Is St. Johns County the largest county in Florida?
No. St. Johns County ranks #44 of 67 in Florida by land area. The largest is Collier County, with 1,997 square miles of land.
What counties border St. Johns County?
St. Johns County shares a land border with Duval County, Clay County, Flagler County, and Putnam County.
What is the population of St. Johns County?
The Census Bureau estimates St. Johns County had 346,328 residents on July 1, 2025, ranking #218 of 3,222 county equivalents. That is 577 people per square mile of land.
What is the county seat of St. Johns County?
The county seat of St. Johns County is St. Augustine.
What cities and towns are in St. Johns County?
St. Johns County has 3 incorporated places. The most populous are St. Augustine city, St. Augustine Beach city, and Marineland town; 323,376 residents live outside any incorporated place.
Is St. Johns County part of a metropolitan area?
Yes. It is a central county of the Jacksonville, FL Metropolitan Statistical Area, which has 5 county equivalents and 1,785,500 residents.
How many ZIP codes are in St. Johns County?
12 ZIP Code Tabulation Areas have land in St. Johns County, and 10 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does St. Johns County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 1.7 times as much land.
How many acres of land are in St. Johns County?
The land measurement converts to approximately 384,422 acres. Including water, total area is approximately 525,780 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.