Cambridge, MA — rate center

NANPA rate center & CO code data, current as of July 28, 2026.

The Cambridge rate center (Massachusetts) anchors 139 active prefixes under area codes 508, 617, 857. Rate centers, not city limits, are what phone numbers are legally tied to.

NANPA records show 139 active prefixes here across 24 carriers. 88 prefixes participate in thousands-block pooling, so blocks of 1,000 numbers are shared between carriers.

The rate center belongs to the Boston-Cambridge-Newton, MA-NH Metropolitan Statistical Area. Routing-wise it sits in LATA 128.

Multiple area codes over one rate center (508/617/857) is the overlay pattern: same geography, different first three digits.

At 139 prefixes — a ceiling of 1,390,000 numbers — Cambridge is one of Massachusetts's heavyweight rate centers.

As always with US numbering: a prefix anchored to Cambridge tells you where the block was issued. The person calling may have ported the number, moved away, or be spoofing it entirely — verify callers through independently found contact details.

Prefixes anchored to Cambridge

FAQ

What area code is Cambridge, MA?

Cambridge is served by 3 area codes — 508, 617, 857 — which overlay the same territory.

How many prefixes does Cambridge have?

139 active NXX prefixes are anchored to this rate center in NANPA records, held by 24 carriers.

Is a call from a Cambridge prefix really from Cambridge?

Not necessarily. The prefix marks where the number block was issued; porting, VoIP and spoofing all detach calls from that geography.