ZIP Code 21045 — Columbia, MD
21045 is a standard (street delivery) ZIP code serving Columbia, Maryland, in Howard 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 21045 at a glance
| ZIP code | 21045 |
|---|---|
| Primary city | Columbia |
| State | Maryland (MD) |
| County | Howard FIPS 24027 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 40,034 |
| Coordinates | 39.206220, -76.827470 |
How ZIP+4 works in 21045
The four digits after the hyphen encode a delivery segment inside 21045. 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 21045 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 Columbia
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 21045.
| ZIP | City | Distance |
|---|---|---|
| 21046 | Columbia, MD | 2.4 mi |
| 21044 | Columbia, MD | 3 mi |
| 21043 | Ellicott City, MD | 3.9 mi |
| 21075 | Elkridge, MD | 4 mi |
| 20794 | Jessup, MD | 4.3 mi |
| 20763 | Savage, MD | 4.7 mi |
| 20723 | Laurel, MD | 5.2 mi |
| 21042 | Ellicott City, MD | 5.7 mi |
| 20701 | Annapolis Junction, MD | 5.7 mi |
| 21076 | Hanover, MD | 6.2 mi |
| 21228 | Catonsville, MD | 6.3 mi |
| 20759 | Fulton, MD | 6.5 mi |
Questions about 21045
What is the ZIP+4 code for 21045?
21045 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 21045, you need to look up a specific street address to get them.
What city is 21045?
21045 is assigned to Columbia, Maryland, in Howard 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.