ZIP Code 80305 — Boulder, CO
80305 is a standard (street delivery) ZIP code serving Boulder, Colorado, in Boulder 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 80305 at a glance
| ZIP code | 80305 |
|---|---|
| Primary city | Boulder |
| State | Colorado (CO) |
| County | Boulder FIPS 08013 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Denver |
| Population | 16,291 |
| Coordinates | 39.977330, -105.248770 |
How ZIP+4 works in 80305
The four digits after the hyphen encode a delivery segment inside 80305. 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 80305 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 Boulder
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 80305.
| ZIP | City | Distance |
|---|---|---|
| 80310 | Boulder, CO | 2 mi |
| 80303 | Boulder, CO | 2 mi |
| 80025 | Eldorado Springs, CO | 4.3 mi |
| 80027 | Louisville, CO | 4.9 mi |
| 80304 | Boulder, CO | 5.2 mi |
| 80301 | Boulder, CO | 5.5 mi |
| 80302 | Boulder, CO | 6.7 mi |
| 80007 | Arvada, CO | 8.1 mi |
| 80026 | Lafayette, CO | 8.3 mi |
| 80021 | Broomfield, CO | 9.3 mi |
| 80471 | Pinecliffe, CO | 9.5 mi |
| 80544 | Niwot, CO | 9.6 mi |
Questions about 80305
What is the ZIP+4 code for 80305?
80305 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 80305, you need to look up a specific street address to get them.
What city is 80305?
80305 is assigned to Boulder, Colorado, in Boulder 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.