The 857 area code covers the same area as 617, including Boston, Cambridge and 23 more places in Massachusetts.
Area code 857 is in Massachusetts, on Eastern Time. In the 857 area, phone numbers are given out most in Suffolk County, then Middlesex and Norfolk counties. It has been in service since May 2, 2001. 617 covers the same area, so two neighbours can have different area codes.
- Where
- 5 counties in Massachusetts, mostly Suffolk County, Middlesex County and Norfolk County
- Time zone
- Eastern Time
- In service since
- May 2, 2001
- Shares its area with
- 617 (since 1947)
- Prefixes in use
- 361
- How to dial
- Local calls need all 10 digits: 857-555-0142.
Find out who called you from an 857 number.
Enter the full 10-digit number to see who it is listed to and the city and state on the listing. It is the same free check as our who called me lookup. To see only the caller ID name on the number, use our free CNAM lookup. To see whether it is a mobile, a landline or a VoIP line, use our free VoIP checker. To see which carrier a (857) number is on today, use our free carrier lookup.
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Boston holds 42% of the phone prefixes in area code 857.
A prefix is the three digits after the area code, and NANPA assigns each one to a town. Counting the 361 prefixes in use shows where 857 numbers are actually given out.
- Boston152 prefixes, 42%
- Cambridge28 prefixes, 8%
- Brookline27 prefixes, 7%
- Roxbury20 prefixes, 6%
- Newton18 prefixes, 5%
- Quincy14 prefixes, 4%
- Dorchester13 prefixes, 4%
- Brighton13 prefixes, 4%
Also served: Jamaica Plain, Milton, Roxbury and Everett and 13 smaller places.
Of the carriers named here, T-Mobile holds the most phone number prefixes in area code 857: 61 of 361.
NANPA, which runs the North American numbering plan, assigns each prefix (the three digits after the area code) to one carrier. Here is how the 361 prefixes in use in 857 divide between carriers; holders this page does not name are grouped as other carriers.
| Carrier | Prefixes | Share |
|---|---|---|
| T-MobileMobile network | 61 | 17% |
| Metro by T-MobileT-Mobile's prepaid brand | 25 | 7% |
| PAETEC (Windstream)Windstream's business phone network | 19 | 5% |
| AT&T MobilityMobile network | 18 | 5% |
| BandwidthSupplies numbers to VoIP and app-based phone services | 10 | 3% |
| Level 3 (Lumen)Lumen's business and wholesale network | 10 | 3% |
| 34 other carriers | 218 | 60% |
98% of these prefixes are pooled, which means the blocks of 1,000 numbers inside them can belong to other carriers. Any number can also have been moved to another carrier since, so this shows who holds the prefixes, not who serves a given number.
Want the carrier of one exact number? Our free carrier lookup checks it, because numbers move between carriers.
Source: NANPA central office code assignments, October 1, 2026.
857 started in 2001 as an overlay on 617, and its ground has not changed since.
2001
857 starts on May 2, 2001, as an overlay on 617: new numbers on the same ground.
An 857 number on your screen can still be a scam, because caller ID is easy to fake.
- Let an unknown call go to voicemail. A real caller leaves a message; a robocaller usually does not.
- Look the number up with the box above before you call back, because calling back tells a robocaller your line is live.
- Hang up on anyone who wants gift cards, crypto or a wire transfer, or asks you to read out a code that was just texted to you.
- Report unwanted robocalls at reportfraud.ftc.gov, or paste a suspicious message into our free scam checker.
The area codes closest to 857 are 781, 978 and 508.
This list measures the distance between the centres of each area, across state lines, and shows codes that share one area together.
Massachusetts has 8 other area codes.
These are the questions people ask most about area code 857.
Where is area code 857?
857 covers Boston, Cambridge, Newton and Quincy and 21 more places in Massachusetts. In the 857 area, phone numbers are given out most in Suffolk County, then Middlesex and Norfolk counties.
What state is area code 857 in?
Massachusetts. 857 is a Massachusetts area code on Eastern Time.
What cities use area code 857?
The places holding the most 857 prefixes are Boston, Cambridge, Newton, Quincy, Brookline, Brighton, Dorchester and Somerville, out of 25 places in all. The count comes from NANPA's prefix assignments as of October 1, 2026.
Which phone company owns area code 857?
No single phone company owns 857. NANPA's records list its 361 prefixes across many carriers, and the ones named on this page include T-Mobile, Metro by T-Mobile and PAETEC (Windstream). Numbers move between carriers, so check one exact number with a carrier lookup.
What time zone is area code 857 in?
857 is on Eastern Time.
When did area code 857 start?
857 went into service on May 2, 2001, as an overlay on 617: new numbers for the same area.
Is 857 the same area as 617?
Yes. 617 (since 1947) covers the same ground as 857. Nobody's number changed when it was added; new lines simply get whichever code has numbers left, so two neighbours can have different codes.
How do I dial an 857 number?
Local calls need all 10 digits: 857-555-0142.
Is 857 a toll-free number?
No. 857 is a regular area code for Boston and Cambridge in Massachusetts, not a toll-free one. The toll-free codes in North America are 800, 833, 844, 855, 866, 877 and 888.
What area codes are near 857?
The closest are 781/339 (Waltham, Massachusetts), 978/351 (Lowell, Massachusetts), 508/774 (Worcester, Massachusetts) and 401 (Providence, Rhode Island), measured between the centres of each area.
Who called me from an 857 number?
Enter the full 10-digit number in the lookup above. It returns the listed owner where there is a public record, where the number is registered, and whether it is a mobile, a landline or a VoIP line.
Is area code 857 a scam?
857 is a real Massachusetts area code, so the code itself is not a warning sign. Scam callers fake local-looking numbers on purpose, so judge the call by what the caller asks for, and look the number up before calling back.
Put this lookup on your site: our free area code widget takes two lines of code and shows any US area code's state, time zone and local time.
Source: NANPA, the North American Numbering Plan Administrator: its area code database and prefix assignments, as of October 1, 2026.