ZIP Code 20166 — Sterling, VA
20166 is a standard (street delivery) ZIP code serving Sterling, Virginia, in Loudoun 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 20166 at a glance
| ZIP code | 20166 |
|---|---|
| Primary city | Sterling |
| State | Virginia (VA) |
| County | Loudoun FIPS 51107 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 14,949 |
| Coordinates | 38.971460, -77.463700 |
How ZIP+4 works in 20166
The four digits after the hyphen encode a delivery segment inside 20166. 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 20166 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 Sterling
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 20166.
| ZIP | City | Distance |
|---|---|---|
| 20148 | Ashburn, VA | 3.9 mi |
| 20170 | Herndon, VA | 4.5 mi |
| 20164 | Sterling, VA | 4.6 mi |
| 20171 | Herndon, VA | 4.8 mi |
| 20147 | Ashburn, VA | 4.9 mi |
| 20151 | Chantilly, VA | 5.3 mi |
| 20152 | Chantilly, VA | 5.8 mi |
| 20194 | Reston, VA | 6.5 mi |
| 20191 | Reston, VA | 6.5 mi |
| 20190 | Reston, VA | 6.8 mi |
| 20165 | Sterling, VA | 6.8 mi |
| 20105 | Aldie, VA | 7.8 mi |
Questions about 20166
What is the ZIP+4 code for 20166?
20166 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 20166, you need to look up a specific street address to get them.
What city is 20166?
20166 is assigned to Sterling, Virginia, in Loudoun 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.