Massachusetts · Eastern Time
857 Area Code
Area code 857 is in Massachusetts, serving Boston and its closest neighbors including Cambridge, Quincy and Newton. It is in the Eastern Time zone. It shares its territory with overlay code 617, so 10-digit dialing is required.
Last updated October 1, 2026 · Source: NANPA
Where is the 857 area code?
857 is a Massachusetts area code covering Boston and its closest neighbors including Cambridge, Quincy and Newton. In the wider directory it sits in the Northeast region.
Cities in the 857 area code
- Boston
- Cambridge
- Quincy
- Newton
- Somerville
- Brookline
- Watertown
- Chelsea
- Everett
- Belmont
- Milton
- Winthrop
Counties served by 857
Suffolk County, Middlesex County and Norfolk County.
857 overlay codes and dialing
The 857 territory is covered by an overlay of 2 area codes: 617, 857. All of them serve the same geographic area, and the original code is 617. Because more than one code covers the same ground, 10-digit dialing is mandatory — you must dial the area code for every local call. New phone lines may be assigned any of these codes.
History of the 857 area code
857 went into service on May 2, 2001 as an overlay of 617, relieving number exhaustion in the Boston area. Rather than splitting the region, the overlay lets existing customers keep their numbers while new lines draw from the added code. Learn more in our overlay guide.
Is 857 a scam or spam risk?
857 is a legitimate geographic area code, not a premium or toll line, so a call from it costs you nothing extra. That said, scammers frequently spoof real local area codes to look familiar on caller ID. A genuine 857 number on your screen is no guarantee the caller is in Boston, MA or trustworthy. See spam & scam-risk area codes for how spoofing works and how to respond.
Other Massachusetts area codes
Explore more
See every code in Massachusetts, compare codes across the Northeast region, or view all Eastern Time codes. You can also browse the 8XX block or the complete numeric list of US area codes.
New to how this all works? Start with how area codes work, then read up on overlays, 10-digit dialing, and spam & scam-risk codes. To check another number, use the area code lookup tool.
Quick answers
857 area code FAQ
Where is the 857 area code?
The 857 area code is in Massachusetts, covering Boston and its closest neighbors including Cambridge, Quincy and Newton, in the Northeast region.
What cities are in the 857 area code?
Cities in the 857 area code include Boston, Cambridge, Quincy, Newton, Somerville, Brookline, Watertown, Chelsea, Everett and Belmont.
What time zone is 857 in?
857 is in the Eastern Time zone.
What is the overlay for the 857 area code?
857 shares its territory with 617. Both codes (617, 857) serve the same area, so 10-digit dialing is required for every call.
When did the 857 area code start?
857 went into service on May 2, 2001 as an overlay of 617.
Do I have to dial 10 digits for 857?
Yes. Because 857 is an overlay area, you must dial the full 10-digit number (area code + 7 digits) for every call.
Is 857 a toll-free or premium code?
No. 857 is a standard geographic area code, so calling it costs the same as any local or long-distance call on your plan. Toll-free calls use 800, 888, 877, 866, 855, 844 or 833.