Area code 857: Massachusetts
Area code 857 is a US state area code for Massachusetts, on Eastern Time. It has 358 prefixes in service across 20 rate centers, the largest being Boston, Cambridge and Brookline. It shares its area with 617, so local numbers there can start with any of them. Local calls there take 10 digits.
Local time in area code 857
America/New_York
Prefixes in service
358 of 792 possible
20 rate centers
Area code 857 facts
| Location | Massachusetts, United States |
|---|---|
| Time zone | Eastern Time |
| Overlays | 617 |
| Overlay of | 617 |
| In service since | May 2, 2001 |
| Local calls | 10 digits; toll calls 1 + 10 digits |
| Carrier | Not shown. An area code is where a number was issued; numbers port between carriers. Check line type |
Which cities and towns use area code 857?
NANPA records each prefix against a rate center, the local billing area a number belongs to, usually named after its main town. These are the 857 rate centers with the most prefixes in service. 8 smaller ones aren't listed.
| Rate center | Prefixes |
|---|---|
| Boston | 150 |
| Cambridge | 27 |
| Brookline | 26 |
| Roxbury | 20 |
| Newton | 18 |
| Quincy | 14 |
| Dorchester | 13 |
| Brighton | 13 |
| Charlestown | 10 |
| Jamaica Plain | 9 |
| Somerville | 8 |
| East Boston | 7 |
Source: NANPA central office code assignments, file dated 10/17/2026. Each prefix holds up to 10,000 numbers.
How do I dial a 857 number?
NANPA's dialling plan for 857: local calls inside the code take 10 digits, toll calls 1 + 10 digits. From another area code, dial 1 first. From abroad, use +1. The examples use 555-0147, from a range reserved for fictional numbers.
| Local call inside 857 | 857-555-0147 |
|---|---|
| From another US or Canadian area code | 1-857-555-0147 |
| From outside North America | +1 857 555 0147 |
| E.164, for CRMs and SMS tools | +18575550147 |
When did area code 857 start?
Area code 857 went into service on May 2, 2001 as an overlay of 617. Today 857 and 617 cover the same area as an overlay, which is why 10-digit dialling is needed for local calls there.
Tools for 857 numbers
- Area code lookup
Look up any code or a whole list of numbers, or find the codes for a state or city.
- Area code time zone
Local time for a list of numbers, with a callable-now flag.
- NPA-NXX lookup
Rate center and state for one prefix, a level below the area code.
- TCPA calling hours checker
Whether it's inside the federal 8 a.m. to 9 p.m. calling window there now.
Next step
A 857 number tells you where it was issued, not what it is now.
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Area code 857 questions
- What state is area code 857?
- Area code 857 is in Massachusetts, United States. Its largest rate centers by number of prefixes are Boston, Cambridge, Brookline, Roxbury and Newton.
- What time zone is area code 857 in?
- Eastern Time.
- What area codes overlay 857?
- 617. An overlay adds a new code to the same area instead of splitting it, so neighbours can have different area codes and local calls need 10 digits.
- When did area code 857 start?
- Area code 857 went into service on May 2, 2001 as an overlay of 617.
- Is an 857 number a cell phone or a landline?
- The area code can't tell you. In the US and Canada mobiles, landlines and VoIP lines share area codes and prefixes, and numbers move between carriers and line types. Only a live line-type lookup answers it for one number.
- How many phone numbers does area code 857 have?
- 358 of its 792 possible prefixes are in service, and each prefix holds up to 10,000 numbers. That counts prefixes assigned to carriers, not numbers in use.
Other area codes in Massachusetts
Sources
Location, overlays, in-service date and dialling plan: NANPA NPA database, file dated 10/16/2026. Prefixes and rate centers: NANPA central office code assignments, 10/17/2026. Time zones mapped to the IANA time zone database. By the SimpleVerifier Team; how we build these pages.