ZIP Code 45312 — Casstown, OH
45312 is a standard (street delivery) ZIP code serving Casstown, Ohio, in Miami 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 45312 at a glance
| ZIP code | 45312 |
|---|---|
| Primary city | Casstown |
| State | Ohio (OH) |
| County | Miami FIPS 39109 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 1,086 |
| Coordinates | 40.060280, -84.079760 |
How ZIP+4 works in 45312
The four digits after the hyphen encode a delivery segment inside 45312. 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 45312 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.
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 45312.
| ZIP | City | Distance |
|---|---|---|
| 45389 | Christiansburg, OH | 2.9 mi |
| 45326 | Fletcher, OH | 5.7 mi |
| 45373 | Troy, OH | 6.4 mi |
| 43072 | Saint Paris, OH | 7.7 mi |
| 45344 | New Carlisle, OH | 8.2 mi |
| 45317 | Conover, OH | 8.4 mi |
| 45349 | North Hampton, OH | 8.8 mi |
| 45371 | Tipp City, OH | 9.5 mi |
| 45356 | Piqua, OH | 10.7 mi |
| 45319 | Donnelsville, OH | 12.3 mi |
| 43070 | Rosewood, OH | 12.8 mi |
| 45372 | Tremont City, OH | 13.1 mi |
Questions about 45312
What is the ZIP+4 code for 45312?
45312 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 45312, you need to look up a specific street address to get them.
What city is 45312?
45312 is assigned to Casstown, Ohio, in Miami 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.