831 area code: location, time zone and numbers
In service since 1998, area code 831 covers San Francisco, California as a US telephone area code.
- Location
- San Francisco, California
- Service start date
- 1998
- The time zone
- Pacific time zone
- Overlay
- None: it is the only code in its area
- Calls inside the area
- Dialling with 7 digits
- Rate centre list
- 24
- Projected exhaustion
- 2078
- Country calling prefix
- +1 (United States)
Source: file of 11/01/2026, drawn from NANPA public reports, the area code report and the rate-centre report; the exhaust year comes from projections by NANPA 2026-1 (April 2026). We are not an official NANPA site.
Get an 831 number
Two routes get you an 831 number. Providers assign a new number together with their plan, and you pick it at sign-up from the numbers they hold in the code. Numbers a seller already holds, often with a pattern, are listed for a one-time price; you then transfer the number to a provider.
Providers, ordered by first-year cost
| Provider | Cheapest plan | First year | Link |
|---|---|---|---|
 Free app | Basic (Just for me), free | $0 | Open Google Voice |
 Free app | Free plan, free | $0 | Open TextNow |
 Developer API | Pay-as-you-go local number, $1.15 a month | $13.80 | Open Twilio |
 Second-number app | Standard, $3.99 a month billed yearly | $47.99 | Open Burner |
 Toll-free specialist | Solo, $6.99 a month billed yearly | $84 | Open UniTel Voice |
 Second-number app | Deluxe (local number), $6.99 a month billed yearly | $102.88 | Open GoDaddy Conversations (formerly Smartline) |
Sellers that list local numbers
| Seller | What it sells | Listed price | Monthly fee | Link |
|---|---|---|---|---|
 Marketplace | Local numbers | From $9 one-time | None stated | Search at Exclusive Digits |
 Marketplace | Local and toll-free | From $9.95 one-time | $2.99 a month | Search at NumberBarn |
 Number broker | Local and toll-free | From $99 one-time | None stated | Search at RingBoost |
 Number broker | Local and toll-free | From $100 one-time | None stated | Search at PhoneNumberExpert |
| 212areacode.comNumber broker | Local numbers | From $150 one-time | None stated | Search at 212areacode.com |
Some sellers and providers may pay us a referral fee. The order never changes, and it is based on first-year cost. How we make money
Places in the 831 area code
For 831, NANPA lists 24 rate centres. Each one is a local calling area, and numbers are assigned to it:
Rate centres: Aptos, Ben Lomond and Big Sur; Boulder Creek, Carmel and Carmel Valley; Castroville, Chualar, Felton and Gonzales; Greenfield (monterey), Hollister and Idria; King City, Monterey, Pinnacles and Salinas; San Ardo, San Juan and San Lucas; Santa Cruz, Soledad, Tres Pinos and Watsonville.
Other related area codes
In California the other area codes are 213, 415, 916, 714, 805, 209, 408, 707, 619, 818, 510, 310, plus 909, 562, 760, 626, 650, 530, 925, 949, 323, 559, 661, 858, 951, 424, 657, 747, 442, 669, 628, 279, 820, 341, 840, 350, 369, 738, 837 and 357.
831 area code questions
Where is area code 831?
Around San Francisco-Oakland-Fremont, CA, 831 rings in San Francisco, California.
What country code goes with a 831 number?
+1. Because 831 belongs to the North American Numbering Plan, callers abroad dial +1 831 plus the 7-digit number.
What time is it in the 831 area code?
The 831 area code uses Pacific time.
Who places calls from a 831 number?
Anyone holding a number in this code may be a home, a mobile, a local business or a caller faking a local number. What a 831 number shows on your screen is where it was assigned, not the person on the line.