County ZIP codes · New Jersey · FIPS 34021
Mercer County, NJ ZIP Codes
Mercer County, New Jersey has 43 ZIP codes (Census 2020 ZCTA-county file; GeoNames postal codes, October 2026): 26 residential and 17 for PO boxes or a single organization. 22 of the residential ones lie mainly in Mercer County and 4 mainly in a neighboring county; 10 cross the county line. Median household income ranges from $50,390 in 08618 (Trenton) to $236,016 in 08558 (Skillman) (Census Bureau, ACS 2020-2024).
- ACS2020-24
- Census2020
Where are the ZIP codes of Mercer County?
Source: U.S. Census Bureau, 2020 ZCTA cartographic boundaries; ACS 2020-2024 5-year estimates (B19013).
How different are its ZIP codes?
The middle half of its ranked ZIP codes (1,000+ people living in households) report median household incomes between $83,906 and $132,520.
They carry 13 postal town names.
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B19013).
All 26 residential ZIP codes in Mercer County
22 ZIP codes lie mainly in Mercer County; 4 more reach into it from a neighboring county and follow the first table.
| In this county | ||||||
|---|---|---|---|---|---|---|
| 08540 | Princeton | 50,388 | 974 | $177k | $768k | 63% |
| 08618 | Trenton | 35,634 | 6,019 | $50k | $227k | 100% |
| 08610 | Trenton | 33,465 | 4,499 | $84k | $265k | 94% |
| 08611 | Trenton | 31,995 | 10,744 | $57k | $161k | 100% |
| 08648 | Lawrence Township | 31,323 | 1,877 | $126k | $428k | 100% |
| 08520 | Hightstown | 29,504 | 1,636 | $118k | $377k | 100% |
| 08619 | Trenton | 24,089 | 2,414 | $106k | $353k | 100% |
| 08638 | Trenton | 22,816 | 4,204 | $67k | $245k | 100% |
| 08550 | Princeton Junction | 21,067 | 1,101 | $224k | $807k | 100% |
| 08690 | Trenton | 18,841 | 2,680 | $127k | $384k | 100% |
| 08691 | Trenton | 16,607 | 685 | $133k | $552k | 89% |
| 08609 | Trenton | 15,938 | 12,111 | $68k | $104k | 100% |
| 08534 | Pennington | 13,272 | 609 | $176k | $573k | 100% |
| 08629 | Trenton | 13,013 | 16,451 | $83k | $182k | 100% |
| 08620 | Trenton | 11,621 | 1,290 | $105k | $374k | 87% |
| 08628 | Trenton | 9,831 | 1,276 | $108k | $370k | 100% |
| 08525 | Hopewell | 4,522 | 202 | $165k | $573k | 70% |
| 08544 | Princeton | 4,392 | 26,458 | – | – | 100% |
| 08560 | Titusville | 3,245 | 244 | $129k | $420k | 99% |
| 08542 | Princeton | 2,533 | 6,562 | $106k | $754k | 100% |
| 08608 | Trenton | 1,250 | 3,956 | $61k | $132k | 100% |
| 08561 | Windsor | 325 | 286 | – | $484k | 100% |
Partly in Mercer County
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates; county shares by land area (Census 2020 ZCTA-county relationship file).
Which ZIP codes cross the county line?
10 ZIP codes of Mercer County extend into another county. A ZIP code follows mail routes, not county borders.
| ZIP | In Mercer | Elsewhere |
|---|---|---|
| 08540 | 63% | Somerset County 26%; Middlesex County 11% |
| 08610 | 94% | Burlington County 6% |
| 08691 | 89% | Monmouth County 11% |
| 08512 | 7% | Middlesex County 93% |
| 08620 | 87% | Burlington County 13% |
| 08530 | 19% | Hunterdon County 81% |
| 08558 | 5% | Somerset County 95% |
| 08501 | 3% | Monmouth County 87%; Burlington County 10% |
| 08525 | 70% | Hunterdon County 30% |
| 08560 | 99% | Hunterdon County 1% |
Source: U.S. Census Bureau, 2020 ZCTA-county relationship file (shares of land area).
PO Box and single-organization ZIP codes
| ZIP | Postal name |
|---|---|
| 08541 | Princeton |
| 08543 | Princeton |
| 08601 | Trenton |
| 08602 | Trenton |
| 08603 | Trenton |
| 08604 | Trenton |
| 08605 | Trenton |
| 08606 | Trenton |
| 08607 | Trenton |
| 08625 | Trenton |
| 08644 | Trenton |
| 08645 | Trenton |
| 08646 | Trenton |
| 08647 | Trenton |
| 08650 | Trenton |
| 08666 | Trenton |
| 08695 | Trenton |
Source: GeoNames postal codes (CC BY 4.0).
Which first three digits do Mercer County's ZIP codes use?
The first three digits of a ZIP code name the sectional center, the mail processing plant that sorts it. Mercer County's ZIP codes use 2 prefixes: 085 and 086.
Source: U.S. Postal Service, labeling list L005 (3-digit ZIP Code prefix groups, SCF sortation), effective October 1, 2026.