Area code 925 serves the inland East Bay region of Northern California. It is associated with Concord, Antioch, Livermore, Pleasanton, San Ramon, Walnut Creek, and nearby communities. The area includes suburban neighbourhoods, business centres, vineyards, open spaces, and employment districts. This guide explains its location, history, time zone, cities, users, and dialling process.
Where Is Area Code 925 Located?
Area code 925 is located in the eastern part of the San Francisco Bay Area. It covers most of Contra Costa County and a smaller inland section of Alameda County.
The code serves the Tri-Valley, San Ramon Valley, central Contra Costa County, and parts of eastern Contra Costa County.
Some of the main cities and communities covered include:
- Antioch
- Brentwood
- Clayton
- Concord
- Danville
- Dublin
- Lafayette
- Livermore
- Martinez
- Moraga
- Orinda
- Pittsburg
- Pleasanton
- San Ramon
- Walnut Creek
The region includes suburbs, historic centres, office districts, healthcare facilities, vineyards, and agricultural land. Area code 925 currently operates without an overlay.
History of Area Code 925
Area code 925 was created through a geographic split of area code 510. It entered service on March 14, 1998. Most of Contra Costa County and inland Alameda County moved to 925, while Oakland, Berkeley, Fremont, and other western East Bay communities remained in 510.
Before 510 existed, the region was part of area code 415, one of California’s original area codes introduced in 1947. The creation of 925 reflected population growth and demand for landlines, mobile phones, fax lines, pagers, and business connections.
Number-conservation programmes later extended the supply by allowing telephone companies to receive smaller number blocks instead of entire prefixes.
Time Zone of Area Code 925
Area code 925 follows the Pacific Time Zone. It observes Pacific Standard Time during standard time and Pacific Daylight Time when daylight saving time is active.
The region is normally three hours behind the Eastern Time Zone. Callers should check the local time before contacting homes, businesses, schools, or public offices.
Major Cities and Their Importance
1. Concord
Concord is one of the largest cities served by area code 925. It is an important commercial and residential centre with shopping areas, healthcare services, offices, schools, transport links, and entertainment venues.
2. Antioch
Antioch is a growing city in eastern Contra Costa County. It has residential communities, schools, healthcare facilities, retail centres, parks, and access to the Sacramento-San Joaquin River Delta.
3. Livermore
Livermore is a major Tri-Valley city known for research, technology, wineries, manufacturing, education, and recreation. Interstate 580 connects it with the Bay Area and Central Valley.
4. San Ramon
San Ramon is a significant business and residential centre. It contains corporate offices, professional services, technology companies, healthcare facilities, schools, parks, and planned neighbourhoods along Interstate 680.
Who Uses Area Code 925?
Area code 925 is used by residents, schools, hospitals, shops, restaurants, wineries, government offices, professional firms, manufacturers, technology companies, logistics providers, and property businesses.
For organisations, a 925 number creates a local connection with the inland East Bay and helps customers identify the service region.
Is Area Code 925 Running Out?
Area code 925 has a substantial supply of telephone numbers remaining. NANPA’s April 2026 forecast projects possible exhaustion during the third quarter of 2051.
The forecast may change as numbers are assigned, returned, or conserved. No overlay is currently in service, and immediate relief is not required.
How to Dial Area Code 925
Callers should include the area code when saving or dialling a 925 number. Use these methods:
- From a landline: Dial 1 + 925 + the seven-digit telephone number.
- From a mobile phone: Dial 925 + the seven-digit number, or 1 + 925 + the number.
- From outside the United States: Dial +1 + 925 + the seven-digit number.
- For emergency and approved short services: Dial numbers such as 911 or 811 directly.
Save complete telephone numbers in contacts, websites, business records, alarms, security systems, and automatic dialling equipment.
Final Thoughts
Area code 925 represents a varied part of the inland East Bay. It connects suburban centres, business districts, historic communities, vineyards, and open landscapes across Contra Costa and Alameda counties.
Since entering service in 1998, 925 has supported residents, employers, schools, healthcare services, and public agencies. With exhaustion projected many years away, it is expected to remain the area’s main telephone identity for decades.
