ZIP Code 81638 — Hamilton, CO
81638 is a standard (street delivery) ZIP code serving Hamilton, Colorado, in Moffat 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 81638 at a glance
| ZIP code | 81638 |
|---|---|
| Primary city | Hamilton |
| State | Colorado (CO) |
| County | Moffat FIPS 08081 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Denver |
| Population | 69 |
| Coordinates | 40.305890, -107.642050 |
How ZIP+4 works in 81638
The four digits after the hyphen encode a delivery segment inside 81638. 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 81638 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 81638.
| ZIP | City | Distance |
|---|---|---|
| 81641 | Meeker, CO | 18.3 mi |
| 81639 | Hayden, CO | 25.9 mi |
| 81625 | Craig, CO | 27.9 mi |
Questions about 81638
What is the ZIP+4 code for 81638?
81638 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 81638, you need to look up a specific street address to get them.
What city is 81638?
81638 is assigned to Hamilton, Colorado, in Moffat 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.