512 Area Code: Austin, Texas and the 737 Overlay

The essentials

512 area code: quick facts

How 512 became Austin's code

1. January 1947: Area code 512 opens. The FCC lists the opening date, and the PUC calls 512 one of the four original Texas codes established in 1947. The PUC says it served most of central and south Texas at the time.
2. November 1992: Area code 210 opens (FCC). The PUC says 210 was placed in service in 1992 for San Antonio and the Rio Grande Valley region.
3. February 1999: Area code 361 opens (FCC). The PUC says the 512 territory became even smaller in 1999, when 361 began for Corpus Christi and the Coastal Bend region.
4. 2000: The PUC orders relief for 512 in Project No. 21772, choosing a concentrated overlay that would have covered only part of the territory. NANPA assigns code 737 in a July 5, 2000 planning letter and schedules mandatory 10-digit dialing for November 10, 2001.
5. April 25, 2001: The PUC announces that number conservation has delayed the need for relief "until possibly 2003" and suspends the 737 plan until further notice (NANPA planning letter PL-276).
6. June 2012: The PUC approves an all-services overlay with code 737 in Project No. 36899. NANPA's planning letter dates the approval June 28, 2012.
7. December 1, 2012: Permissive 10-digit dialing begins. Local calls can be dialed with seven or ten digits.
8. June 1, 2013: Ten-digit dialing becomes mandatory for local calls in the 512 area.
9. July 1, 2013: Telephone providers can issue new numbers with the 737 area code. The FCC lists 737 as opened in July 2013.

Where area code 512 is used

The PUC's May 2013 release says area code 512 serves Travis, Williamson, Hays, Burnet, Lampasas, Caldwell, Bastrop, Lee, Milam, Mills, Coryell, San Saba, Bell, Fayette, Guadalupe, Comal, Blanco, Llano, and Burleson counties. The release does not say which of these counties are covered in full and which only in part. NANPA's 2012 planning letter says the 512 area lies "principally" in Bastrop, Burnet, Caldwell, Hays, Lampasas, Milam, Travis, and Williamson counties.

The same NANPA letter names communities served by 512, including Austin, Bastrop, Bee Cave, Buda, Burnet, Cedar Park, Dripping Springs, Elgin, Georgetown, Hutto, Kyle, Lakeway, Lampasas, Leander, Lockhart, Manor, Pflugerville, Round Rock, San Marcos, Smithville, Taylor, West Lake Hills, and Wimberley. It says 737 serves the same geographic area as 512.

The PUC's list of 512 prefixes, in a 2025 archived copy that reflects NANPA data through November 2023, shows 512 numbers assigned to rate centers including Austin, Bastrop, Bertram, Buda, Burnet, Dripping Springs, Elgin, Georgetown, Granger, Hutto, Jarrell, Kyle, Lampasas, Leander, Liberty Hill, Lockhart, Rockdale, San Marcos, Smithville, Taylor, and Wimberley. A rate center is a billing area, not a boundary. Confirm a specific address with your phone provider.

Why 512 added 737

The PUC's May 2013 release says the new code was "needed to handle regional growth along with the added demand for new wireless phone numbers and business landlines," and that the remaining 512 numbers were forecast to last until late 2013.

The road to 737 was long. NANPA first filed a relief petition for 512 on March 1, 2000. The PUC ordered a concentrated overlay, along with measures to slow the use of numbers: thousand-block number pooling, a cap on the central office codes a provider could obtain, and reclamation of unused numbers. Those measures worked well enough that the PUC suspended the plan in April 2001.

PUC staff reopened the question in 2009 in Project No. 36899. NANPA filed a new petition on January 26, 2010, with industry consensus for an all-services overlay, but the project was put on hold again because conservation was again delaying exhaust. In April 2012 a new forecast moved the projected exhaust date for 512 to the fourth quarter of 2013, and the PUC adopted a 13-month schedule ending in July 2013.

According to the PUC order, the all-services overlay had a projected life of 33 years. NANPA had also offered four concentrated overlay options, but the order says each would have left the outer parts of the 512 territory with only two to six years of numbers. The order notes that most of the public e-mails it received preferred keeping Austin on 512 and moving the surrounding communities to 737, but the commission chose the overlay.

NANPA's April 2026 analysis projects that the 512/737 area will run out of numbers in the first quarter of 2044, based on data as of March 1, 2026. Its October 2025 analysis had projected the third quarter of 2042. Forecasts move from one analysis to the next, so treat the date as an estimate.

Neighboring area codes around Austin

The table shows how each code relates to 512, based on the PUC, NANPA, and FCC sources in this guide. Other codes serve areas outside the sources checked, so the table does not claim to show every neighbor.

The overlay code that shares 512's territory

An overlay adds a new area code to the same geographic area, so existing numbers do not change. One overlay code serves the Austin area alongside 512:

• 737 (approved June 2012; numbers from July 1, 2013): an all-services overlay on the whole 512 territory. The PUC said it was the twenty-fifth area code in Texas and the first one introduced in ten years.

The PUC says current customers in the 512 area kept their 512 numbers, and new customers could be assigned numbers with either the 737 or the 512 area code. Because the codes overlap, two neighbors on the same street can have different area codes. The PUC credited number conservation measures such as number pooling with reducing the need to launch new area codes as rapidly as in the 1990s.

Time zone and daylight saving time

Area code 512 uses Central Time. The tz database lists America/Chicago as "Central (most areas)". Federal rules for the boundary between the Central and Mountain zones (49 CFR 71.7) run along the east line of Hudspeth County in far west Texas, and the Austin area lies east of that line.

NIST says daylight saving time begins at 2:00 a.m. on the second Sunday of March and ends at 2:00 a.m. on the first Sunday of November. The NIST page lists Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands, and Arizona as places that do not observe it, and Texas is not on that list. In 2026, NIST gives March 8 and November 1 as the change dates.

How to dial a 512 number

North American numbers have three parts: a country code, a three-digit area code, and a seven-digit local number. NANPA says the ITU assigned country code 1 to the NANP area. The PUC says customers in the 512 area must dial 10 digits (area code plus phone number) for all local calls, a rule in force since June 1, 2013. NANPA's planning letter lists 1 plus 10 digits for toll calls and 0 plus 10 digits for operator-assisted, collect, and credit card calls.

The PUC's customer fact sheet on area codes advises updating printed materials, reprogramming speed dial numbers, and asking your alarm company whether a home alarm system needs to be reprogrammed. Alarm panels were a real concern in Austin: the PUC order notes that the Texas Burglar and Fire Alarm Association asked for a longer permissive dialing period so panels could be reprogrammed or replaced.

Caller ID and scams with a 512 number

The FTC warns that "Scammers can make any name or number show up on your caller ID." That is called spoofing. Scammers can also match the first six digits of your own number, which the FTC calls neighbor spoofing.

• If you pick up and do not recognize the caller, the FTC advises that you hang up.
• Letting an unknown call go to voicemail is one option.
• The FTC says call blocking is your best defense against unwanted calls.

The sources checked do not say that 512 numbers are targeted more than others. A 512 number shows the code that was assigned, not who is calling or where they are. Because 737 shares the same region, and because spoofed numbers can show any code, a 512 caller ID is not a reliable sign that the caller is in Austin.

Choosing a 512 number for a business

512 is the original Austin area code, but the PUC says new customers could be assigned numbers with either 737 or 512. A new line may carry 737 instead of 512, and the area code does not show which part of the region the business is in.

Because the codes share territory, route calls by team or extension, not by area code. Ask your provider which code a new line gets, since that depends on its current inventory.

Whether a specific 512 number can be assigned to your business depends on your phone provider and its current inventory. This guide does not make claims about availability.

Important: Confirm availability with your provider before you plan a campaign or print a number on materials.

Before you use a 512 number

• Confirm the number is available from your provider, and get its terms in writing.
• Ask who owns the number and whether it can be moved to another provider if you switch.
• Confirm which area code your line uses. 512 and 737 serve the same region.
• Set 10-digit dialing for numbers in both codes before you go live, because the PUC requires 10 digits for all local calls in the 512 area.
• Update printed materials, speed dial entries, and alarm or other equipment that stores numbers, as the PUC advises, and print the full 10-digit number with the area code.
• Route calls by team or extension, because 512 and 737 share one territory.
• Plan for caller ID. A 512 number does not prove who is calling, and neighbor spoofing copies the first six digits of your own number.

Related guides and tools

• VoIP phone service in Austin, TX: our guide to business phone service for Austin companies.
• 214 area code guide: Dallas, another Texas metro, where four codes share one region.
• 713 area code guide: Houston, another original 1947 Texas code, for comparison with Austin.
• 210 area code guide: San Antonio, a neighboring Central Texas metro, for comparison with Austin.
• 817 area code guide: Fort Worth, another Texas metro, for comparison with Austin.
• What is a DID number?: what a DID is, local versus toll-free types and porting rules.
• Business phone number porting: how number porting works, how long it takes and how to prepare.
• Full list of U.S. area codes by state, with the overlay codes and time zone for every code.
• Browse all U.S. area code guides, including overlay codes that do not have their own guide yet.
• Business phone system and call routing for local numbers in Austin.

Frequently asked questions