---
title: "Area code 510: California, United States"
url: "https://lookvalid.com/area-code/510.md"
canonical_url: "https://lookvalid.com/area-code/510"
last_updated: "2026-10-23"
type: "reference"
summary: "Area code 510 serves California, United States. Number formats, numbering rules, a live phone validator and the other codes in California."
---

# Area code 510: California, United States

Area code 510 serves California, United States. Number formats, numbering rules, a live phone validator and the other codes in California.

NANPA lists 785 central office codes (prefixes) in use in area code 510, held by 31 holders across 13 rate centers.
Pacific Bell holds the most prefixes, 277 (35%). 65% of the prefixes are pooled, which means their thousands-blocks can belong to different companies.
The FCC unwanted-call data has 4,286 complaints on file for 2,800 numbers in 510, most often filed as "Unwanted Calls". These are consumer reports, not findings.

## Facts

- In service since: 1991-09-02
- Time zone: Pacific (P)
- Assigned overlays: 341 (2019-07-22)
- Prefixes in use: 785
- Pooled prefixes: 514 (65%)
- Rate centers: 13
- Companies holding prefixes: 31
- Assignment dates on file: 2001-01-25 to 2026-02-25 (191 prefixes)
- ZIP codes in its places: 15

## Rate centers

| Rate center | Prefixes | Share |
| --- | --- | --- |
| OKLD MN-PD | 204 | 26% |
| HAYWARD | 117 | 15% |
| FRNK MAIN | 81 | 10% |
| OKLD BKLY | 70 | 9% |
| OKLD TRNID | 60 | 8% |
| RICHMOND | 53 | 7% |
| FRNK OLIVR | 45 | 6% |
| OKLD ALMD | 42 | 5% |
| 5 other rate centers | 113 | 14% |

## Carriers

| Holder | Prefixes | Share |
| --- | --- | --- |
| Pacific Bell | 277 | 35% |
| New Cingular Wireless PCS | 78 | 10% |
| T-Mobile USA | 65 | 8% |
| Verizon Wireless | 60 | 8% |
| Mcimetro Access Transmission Services | 48 | 6% |
| Metropcs | 45 | 6% |
| 25 other carriers | 212 | 27% |

A prefix holder is the company a code was assigned to, not necessarily a number's current carrier, because numbers can be ported to another company.

## History

- 1947-01-01: Area code 415, named as the parent of 510 in the NANPA report, was in service.
- 1991-09-02: Area code 510 went into service.
- 1998-03-14: Area code 925 went into service and names 510 as its parent.
- 2019-07-22: Area code 341 went into service as an overlay in the same area as 510.

## Nearest area codes

The area codes closest to 510, measured between the centers of the ZIP code places they serve, are 925 (about 13 miles), 415 (about 25 miles), 628 (about 25 miles), 650 (about 25 miles) and 669 (about 43 miles).

## ZIP codes

15 ZIP codes fall in places that have a rate center in this area code. The places with the most are Hayward, CA (7 ZIP codes), Richmond, CA (7 ZIP codes) and Crockett, CA (1 ZIP code). A ZIP code and an area code are unrelated systems, so a ZIP code can sit in more than one area code and an area code spans many ZIP codes.

## Complaints on file

4,286 complaints for 2,800 numbers. Numbers whose latest complaint falls in each year:

- 2023: 142
- 2024: 91
- 2025: 114

## Questions

### Where is area code 510?

NANPA assigns area code 510 to California, United States.

### In which state does area code 510 sit?

California. 510 is one of 41 area codes the NANPA table assigns to the state.

### Which places does area code 510 cover?

The places with the most ZIP codes among the rate centers in 510 are Hayward, CA, Richmond, CA and Crockett, CA. The rate center list on this page shows all of them.

### Who owns area code 510?

NANPA assigns area codes. Within 510, Pacific Bell holds the most prefixes, 277 prefixes or 35%.

### Which time zone does 510 use?

The NANPA NPA report lists the time zone for 510 as Pacific (P).

### What year did 510 enter service?

The NANPA NPA report gives an in-service date of 1991-09-02, so 510 has been in use since 1991.

### Does area code 510 have an overlay?

Yes. 341 (in service 2019-07-22) shares the same area with 510, so numbers from all of them are local to each other.

### Which area codes are nearest to 510?

The area codes closest to 510, measured between the centers of the ZIP code places they serve, are 925 (about 13 miles), 415 (about 25 miles), 628 (about 25 miles), 650 (about 25 miles) and 669 (about 43 miles).

### How many prefixes does area code 510 have?

NANPA's report dated 2026-10-17 lists 785 prefixes in service in 510, spread over 13 rate centers and 31 holders.

### Are there complaints about 510 numbers?

The FCC data on file has 4,286 complaints for 2,800 numbers in 510. They are unverified consumer reports. A number with no complaints on file is not proven safe.

Sources: NANPA central office code report dated 2026-10-17; NANPA NPA report dated 2026-10-18; FCC unwanted-call complaints, data fetched 2026-10-17; ZIP code places from GeoNames (CC BY 4.0).