ZIP Code 01821 — Billerica, MA
01821 is a standard (street delivery) ZIP code serving Billerica, Massachusetts, in Middlesex 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 01821 at a glance
| ZIP code | 01821 |
|---|---|
| Primary city | Billerica |
| State | Massachusetts (MA) |
| County | Middlesex FIPS 25017 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 30,143 |
| Coordinates | 42.549990, -71.252060 |
How ZIP+4 works in 01821
The four digits after the hyphen encode a delivery segment inside 01821. 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 01821 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 01821.
| ZIP | City | Distance |
|---|---|---|
| 01862 | North Billerica, MA | 2.7 mi |
| 01730 | Bedford, MA | 3.7 mi |
| 01803 | Burlington, MA | 4.1 mi |
| 01887 | Wilmington, MA | 4.5 mi |
| 01876 | Tewksbury, MA | 4.5 mi |
| 01741 | Carlisle, MA | 5.2 mi |
| 01824 | Chelmsford, MA | 6 mi |
| 01852 | Lowell, MA | 6.1 mi |
| 01731 | Hanscom Afb, MA | 6.1 mi |
| 02420 | Lexington, MA | 6.6 mi |
| 01801 | Woburn, MA | 6.6 mi |
| 01851 | Lowell, MA | 7 mi |
Questions about 01821
What is the ZIP+4 code for 01821?
01821 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 01821, you need to look up a specific street address to get them.
What city is 01821?
01821 is assigned to Billerica, Massachusetts, in Middlesex 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.