ZIP Code 18103 — Allentown, PA
18103 is a standard (street delivery) ZIP code serving Allentown, Pennsylvania, in Lehigh County. To mail something here you only need these five digits — but the four-digit extension narrows delivery to a single point, and it is what USPS bulk postage discounts are priced on.
ZIP code 18103 at a glance
| ZIP code | 18103 |
|---|---|
| Primary city | Allentown |
| State | Pennsylvania (PA) |
| County | Lehigh FIPS 42077 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 48,746 |
| Coordinates | 40.572230, -75.481380 |
How ZIP+4 works in 18103
The four digits after the hyphen encode a delivery segment inside 18103. In practice one segment usually means:
- One side of one block — odd numbers on a street between two cross streets
- A single large building, or one floor of it
- A group of PO boxes, sometimes a single box
- A single business that receives enough mail to warrant its own code
That is why 18103 has no single ZIP+4: two neighbors across the street from each other usually have different ones. Enter a street address above and we will return the exact nine-digit code along with the standardized USPS address format.
Other ZIP codes in Allentown
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 18103.
| ZIP | City | Distance |
|---|---|---|
| 18101 | Allentown, PA | 2.2 mi |
| 18102 | Allentown, PA | 2.5 mi |
| 18049 | Emmaus, PA | 3.8 mi |
| 18034 | Center Valley, PA | 4 mi |
| 18104 | Allentown, PA | 4.4 mi |
| 18046 | East Texas, PA | 4.5 mi |
| 18109 | Allentown, PA | 4.9 mi |
| 18018 | Bethlehem, PA | 5.9 mi |
| 18032 | Catasauqua, PA | 5.9 mi |
| 18052 | Whitehall, PA | 6 mi |
| 18106 | Allentown, PA | 6 mi |
| 18015 | Bethlehem, PA | 6.1 mi |
Questions about 18103
What is the ZIP+4 code for 18103?
18103 is the five-digit ZIP code. The ZIP+4 adds four more digits that identify a specific delivery point — usually one side of a city block, a single building, or a group of PO boxes. Because those four digits change from address to address within 18103, you need to look up a specific street address to get them.
What city is 18103?
18103 is assigned to Allentown, Pennsylvania, in Lehigh County.
Do I need to use the ZIP+4?
It is optional for ordinary mail, but it speeds up sorting and it is required for most USPS bulk-mail postage discounts. Many address-verification and e-commerce systems also use ZIP+4 to confirm a delivery point exists.
Need thousands of these?
Upload a CSV and get ZIP+4, county, carrier route, and delivery-point data appended to every row — or call the API directly.