ZIP Code 20818 — Cabin John, MD
20818 is a standard (street delivery) ZIP code serving Cabin John, Maryland, in Montgomery 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 20818 at a glance
| ZIP code | 20818 |
|---|---|
| Primary city | Cabin John |
| State | Maryland (MD) |
| County | Montgomery FIPS 24031 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 1,539 |
| Coordinates | 38.973470, -77.161880 |
How ZIP+4 works in 20818
The four digits after the hyphen encode a delivery segment inside 20818. 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 20818 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 20818.
| ZIP | City | Distance |
|---|---|---|
| 20812 | Glen Echo, MD | 1.1 mi |
| 20817 | Bethesda, MD | 1.8 mi |
| 22101 | Mclean, VA | 2.4 mi |
| 20816 | Bethesda, MD | 2.6 mi |
| 20894 | Bethesda, MD | 3.6 mi |
| 20892 | Bethesda, MD | 3.6 mi |
| 20814 | Bethesda, MD | 3.8 mi |
| 22102 | Mclean, VA | 3.9 mi |
| 20889 | Bethesda, MD | 4.3 mi |
| 20815 | Chevy Chase, MD | 4.5 mi |
| 20016 | Washington, DC | 4.5 mi |
| 22207 | Arlington, VA | 5 mi |
Questions about 20818
What is the ZIP+4 code for 20818?
20818 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 20818, you need to look up a specific street address to get them.
What city is 20818?
20818 is assigned to Cabin John, Maryland, in Montgomery 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.