ZIP Code 98040 — Mercer Island, WA
98040 is a standard (street delivery) ZIP code serving Mercer Island, Washington, in King 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 98040 at a glance
| ZIP code | 98040 |
|---|---|
| Primary city | Mercer Island |
| State | Washington (WA) |
| County | King FIPS 53033 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Los_Angeles |
| Population | 25,307 |
| Coordinates | 47.566110, -122.232000 |
How ZIP+4 works in 98040
The four digits after the hyphen encode a delivery segment inside 98040. 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 98040 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 98040.
| ZIP | City | Distance |
|---|---|---|
| 98118 | Seattle, WA | 2.4 mi |
| 98144 | Seattle, WA | 3.1 mi |
| 98004 | Bellevue, WA | 3.8 mi |
| 98006 | Bellevue, WA | 3.9 mi |
| 98108 | Seattle, WA | 4.1 mi |
| 98056 | Renton, WA | 4.2 mi |
| 98122 | Seattle, WA | 4.2 mi |
| 98005 | Bellevue, WA | 4.5 mi |
| 98039 | Medina, WA | 4.6 mi |
| 98178 | Seattle, WA | 4.7 mi |
| 98134 | Seattle, WA | 4.9 mi |
| 98104 | Seattle, WA | 5.1 mi |
Questions about 98040
What is the ZIP+4 code for 98040?
98040 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 98040, you need to look up a specific street address to get them.
What city is 98040?
98040 is assigned to Mercer Island, Washington, in King 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.