ZIP Code 78663 — Round Mountain, TX
78663 is a standard (street delivery) ZIP code serving Round Mountain, Texas, in Blanco 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 78663 at a glance
| ZIP code | 78663 |
|---|---|
| Primary city | Round Mountain |
| State | Texas (TX) |
| County | Blanco FIPS 48031 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Chicago |
| Population | 503 |
| Coordinates | 30.415820, -98.311440 |
How ZIP+4 works in 78663
The four digits after the hyphen encode a delivery segment inside 78663. 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 78663 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 78663.
| ZIP | City | Distance |
|---|---|---|
| 78657 | Horseshoe Bay, TX | 9 mi |
| 78636 | Johnson City, TX | 9.6 mi |
| 78669 | Spicewood, TX | 10.8 mi |
| 78654 | Marble Falls, TX | 12.3 mi |
| 78620 | Dripping Springs, TX | 17 mi |
| 78639 | Kingsland, TX | 18.8 mi |
| 78635 | Hye, TX | 20.1 mi |
| 78645 | Leander, TX | 20.5 mi |
| 78738 | Austin, TX | 20.6 mi |
| 78734 | Austin, TX | 21.8 mi |
| 78675 | Willow City, TX | 23.6 mi |
| 78606 | Blanco, TX | 24 mi |
Questions about 78663
What is the ZIP+4 code for 78663?
78663 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 78663, you need to look up a specific street address to get them.
What city is 78663?
78663 is assigned to Round Mountain, Texas, in Blanco 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.