Area codes · +1
Area code 857
Area code 857 is centred on Boston, Massachusetts. We hold 3,846 allocated blocks for it across 21 rate centres, split 51% mobile, 32% landline and 18% VoIP.
The other area codes laid over 857
Area code 857 does not have Boston to itself. 1 other code — 617 — serves the same rate centres, laid over the same ground rather than dividing it. That is an overlay: a new code added when the old one ran out of numbers, covering the same streets. Two neighbours can hold different area codes, so the code says roughly when a number was issued rather than where it sits.
6174,788 blocks, 27 rate centres, mostly landline
Each holds its own blocks and its own carrier mix, so a 857 number and a 617 number from the same street can report different line types. Filtering Boston by area code needs all 2 of them.
857 is not confined to Boston itself: its blocks sit across 21 rate centres, named in the table below.
Massachusetts is split across 9 area codes — 978, 781, 774, 508, 413, 857 and others. By allocated blocks 857 is the 7th largest of them, holding 10% of the Massachusetts total.
Where 857 numbers are concentrated
NANPA truncates rate-centre names to ten characters and drops the spaces, which is why Quincy and Jamaica Pl are shortened. Names are reproduced as recorded rather than expanded — the abbreviation is the key the block data is filed under.
| Rate centre | Blocks | Share of 857 |
|---|---|---|
| Boston | 1,601 | 42% |
| Cambridge | 293 | 8% |
| Brookline | 287 | 7% |
| Roxbury | 220 | 6% |
| Newton | 198 | 5% |
| Quincy | 154 | 4% |
| Brighton | 143 | 4% |
| Dorchester | 140 | 4% |
| Charlestn | 104 | 3% |
| Jamaica Pl | 96 | 2% |
| Somerville | 81 | 2% |
| Eastboston | 77 | 2% |
| Belmont | 73 | 2% |
| Watertown | 63 | 2% |
| Winthrop | 58 | 2% |
| So Boston | 55 | 1% |
| Hyde Park | 50 | 1% |
| Everett | 44 | 1% |
| Milton | 44 | 1% |
| Chelsea | 41 | 1% |
| Xxxxxxxxxx | 1 | 0% |
Carriers holding the most 857 blocks
Onvoy663 blocks
Verizon Wireless618 blocks
Omnipoint Miami E License, Llc391 blocks
T-Mobile USA, Inc.326 blocks
Metro by T-Mobile208 blocks
AT&T Wireless199 blocks
The largest holder, Onvoy, has 17% of the code.
These are original allocations. A number keeps its digits and its block when its subscriber moves network, so a ported 857 number still reports the carrier it started with. Closing that gap needs a live query against the routing database. How line type is derived.
Check a single 857 number, or run a whole list through the free cleaner — neither uploads anything.
Common questions
Where is area code 857?
Area code 857 covers Boston, Massachusetts. It is not the only code there: 617 is an overlay on the same rate centres, so a Boston, Massachusetts number can start with any of them.
Is a 857 number a mobile or a landline?
It can be either, and the digits do not say which. North American mobile and landline numbers share the same ranges, so the answer comes from the carrier holding the block. In 857 the split runs 51% mobile, 32% landline and 18% VoIP, so mobile is the most likely single answer.
Which carriers hold 857 numbers?
The largest holders are Onvoy, Verizon Wireless, Omnipoint Miami E License, Llc. That is the carrier the block was allocated to, which is not necessarily the network a given number sits on today.
How many 857 numbers are there?
The code holds 3,846 allocated blocks in our copy of the numbering plan. A block is 1,000 or 10,000 consecutive numbers depending on how deeply it has been pooled, so 857 covers on the order of 3,846,000 possible numbers — most of which have never been issued to anyone.