ZIP Code 94027 — Atherton, CA
94027 is a standard (street delivery) ZIP code serving Atherton, California, in San Mateo 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 94027 at a glance
| ZIP code | 94027 |
|---|---|
| Primary city | Atherton |
| State | California (CA) |
| County | San Mateo FIPS 06081 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Los_Angeles |
| Population | 7,002 |
| Coordinates | 37.453990, -122.203130 |
How ZIP+4 works in 94027
The four digits after the hyphen encode a delivery segment inside 94027. 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 94027 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 94027.
| ZIP | City | Distance |
|---|---|---|
| 94025 | Menlo Park, CA | 1.1 mi |
| 94061 | Redwood City, CA | 1.9 mi |
| 94063 | Redwood City, CA | 2.8 mi |
| 94301 | Palo Alto, CA | 3 mi |
| 94305 | Stanford, CA | 3.2 mi |
| 94304 | Palo Alto, CA | 4.4 mi |
| 94303 | Palo Alto, CA | 4.6 mi |
| 94070 | San Carlos, CA | 4.7 mi |
| 94306 | Palo Alto, CA | 4.7 mi |
| 94062 | Redwood City, CA | 5.5 mi |
| 94028 | Portola Valley, CA | 5.5 mi |
| 94065 | Redwood City, CA | 6.1 mi |
Questions about 94027
What is the ZIP+4 code for 94027?
94027 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 94027, you need to look up a specific street address to get them.
What city is 94027?
94027 is assigned to Atherton, California, in San Mateo 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.