North American Numbers Source-cited · ownership disclosed
Area code
925
In service
United States · since 1998

Concord / Walnut Creek

Area code 925 serves the inland East Bay, covering the inland portions of Contra Costa and Alameda Counties, including Concord, Walnut Creek, and Livermore. It was split from 510 in 1998 and has no overlay.

The essentials Numbering data · NumberResearch · as of 2026-09-18
Place
Concord / Walnut Creek
Type
geographic
Status
in service
In service since
1998
Projected exhaust
2051 Q3

Status, dates and counts are read from NumberResearch (NANPA / CNAC / FCC records). Assignment records show initial assignees, not the carrier serving a number today.

A · Where it is

Where 925 is

Inland Contra Costa County and inland Alameda County (east of the Berkeley Hills)..

Communities served wholly or partly by 925:

ConcordWalnut CreekLivermorePleasantonDublinSan RamonDanvilleAntioch

Representative list; many additional inland East Bay communities are served.

B · Relationships

How it relates to other codes

The codes 925 was split from, spawned, or shares its area with. A split divides the map and changes some numbers; an overlay shares the same ground and changes none — what's the difference?

Split from · 1998 510 Oakland Split from 510 on March 14, 1998, divided along the Berkeley Hills.
Related 707 Santa Rosa / North Bay Adjacent to the north (707/369).
Related 209 Stockton Adjacent to the east (209/350).
Related 408 San Jose Adjacent to the south (408/669).
What's changing. No overlay; ten-digit dialing mandatory since October 24, 2021. (A code 926 was long reserved as potential relief but has NOT been activated.)
C · History

How 925 got here

1998-03-14
Area code 925 established via split from 510, divided along the Berkeley Hills boundary.
Source: Wikipedia
2021-10-24
Transitioned to ten-digit dialing (988 lifeline designation).
Source: Wikipedia
D · Capacity

How full it is

Prefixes assigned
655
Prefixes available
145
Thousands-blocks assigned
2,934

Prefix-assignment counts describe allocation to carriers, not how many individual numbers are in use. Full technical records: NumberResearch ↗.

Compare 925 with another code →
Sources
Wikipedia ↗
Area code 925
NumberResearch.org ↗
Live status, dates, assignment counts and exhaust forecast — data as of 2026-09-18 (CC BY 4.0).

Place, relationships and history above are compiled by North American Numbers from the sources listed and last checked 2026-09-18. A check date is not an expert review — see how this is made. Flag an error.