Area code 310 – California
310 has served California since 1991, split from 213. All but a handful of its 786 number blocks are allocated (786 of 786), so it is effectively exhausted. AT&T is the largest holder with 43.6% of blocks, ahead of Frontier at 17.4%. It shares its geography with overlay codes 424, so local calls take all ten digits. FTC complaints naming a 310 caller ID totalled 454 in the 33 days to 30 October 2026 (227th of 422 ranked codes). The dominant complaint type is “Other”.
- State
- California
- In service since
- 1991
- Time zone
- Pacific
- Shares area with
- 424
Who holds 310 number blocks
Share of the 786 assigned NXX blocks (100% of the 786 possible), across 25 carriers. This is share of number blocks, not of subscribers.
- AT&T43.6%
- Frontier17.4%
- Verizon13%
- T-Mobile9.2%
- Lumen3.9%
- Spok3.1%
- TPx3.1%
- Onvoy2.2%
- Other CLEC / VoIP2.2%
- American Messaging1.4%
- Bandwidth0.6%
- Peerless0.3%
- Windstream0.1%
Spam complaints naming 310
FTC Do Not Call complaints where the caller ID was a 310 number, 28 Sep – 30 Oct 2026 (33 days). Caller IDs on spam calls are frequently spoofed, so these are complaints about the code, not calls proven to originate in it.
Rate centers in 310
NANPA allocates number blocks to rate centers and records their names abbreviated to ten characters, so these are NANPA's codes rather than place names – CHAMPAURBN is Champaign-Urbana, NWYRCYZN01 is a New York City zone. We show them unchanged instead of guessing at the full names. Showing the largest 5 of 17.
Timeline
- 1991 310 goes into service, split from or overlaid on 213.
More about 310
Separate pages for the questions that need their own answer: what time it is there, what the complaint data says, who holds the number blocks, and how the code compares with the one it shares its area with.
Frequently asked about 310
What state is area code 310?
California. It covers the same area as 310/424.
Can I still get a 310 number?
Only from recycled stock. 786 of the 786 available blocks are already allocated, so new numbers in the area normally come from the overlay codes (310/424).
Is a call from 310 a scam?
Not by itself. 310 drew 454 FTC complaints in the 33 days to 30 October 2026, 227th of 422 ranked codes – mid-pack or lower. Spam callers spoof caller IDs, so the only useful check is the full number. The most reported category here is “Other”.
Which carrier owns 310 numbers?
AT&T holds the largest share of assigned number blocks at 43.6%. The rest is spread across 3 other carriers. This is share of number blocks, not of subscribers – people keep their numbers when they switch carriers.
Do I need to dial 10 digits in 310?
NANPA records the local dialing plan for 310 as “1+10D”.
Sources and verification
- NANPA – NPA Database (npa_report.csv), file date 11/01/2026, retrieved Nov 1, 2026
- NANPA – CO Code Assignment Records, All States (utilized), file updated 11/01/2026, retrieved Nov 1, 2026
- FTC – Do Not Call Reported Calls Data, 25 daily files 28 Sep – 30 Oct 2026, retrieved Nov 1, 2026
NANPA dialing note for this code: “1+10D”. Reviewed by the data desk. Spotted an error? Request a correction.