Understanding Area Code 713: Houston's Original Phone Code

Area code 713 serves as Houston, Texas's original telephone area code, established in 1947 as part of the initial North American Numbering Plan (NANP). The NANP, designed by AT&T and Bell Laboratories, standardized telephone numbering across the United States and Canada to enable direct distance dialing without operator assistance. Today, you'll find it sharing the Houston metropolitan area with four overlay codes: 281, 832, 346, and 621.

What is an overlay code? An overlay is when multiple area codes serve the same geographic region simultaneously. Unlike geographic splits (which divide a region into smaller areas with different codes), overlays allow new phone numbers to be assigned with any of the area codes regardless of specific location. This approach keeps communities together while providing sufficient phone numbers to meet demand. The trade-off is that all local calls require 10-digit dialing.

Area Code 713 History and Evolution

Each area code in the NANP provides up to 7,920,000 theoretical phone numbers (792 prefixes × 10,000 numbers per prefix). Reserved test numbers and technical requirements reduce this count in practice. As Houston's population and telecommunications demands grew – driven by cell phones, fax machines, pagers, and the inefficient block-assignment system (which allocates numbers in blocks of 10,000 even when fewer are needed) – the region repeatedly approached number exhaustion, necessitating splits and overlays.

1947: Original Implementation

When AT&T introduced the North American Numbering Plan in October 1947, area code 713 covered the entire southeastern quarter of Texas – a massive geographic region spanning from the Gulf Coast to East Texas. Texas was initially divided into four numbering plan areas: 214, 512, 713, and 915.

March 19, 1983: First Split – Area Code 409

As Houston's population exploded through the 1970s and early 1980s, the region approached exhaustion of available phone numbers. Area code 409 split off on March 19, 1983, serving the Gulf Coast region (including Galveston and Beaumont) while 713 focused on the Houston metropolitan area. This geographic split preserved seven-digit dialing within each region.

November 2, 1996: Second Split – Area Code 281

Houston's continued growth demanded another expansion. Area code 281 launched on November 2, 1996, as a geographic split serving suburban areas while 713 remained in central Houston. This split maintained seven-digit local dialing within each zone.

January 16, 1999: First Overlay – Area Code 832

Rather than continue geographic splits – which would create increasingly small regions and cause confusion – regulators implemented area code 832 as an overlay on January 16, 1999. According to the Public Utility Commission of Texas, overlays let customers keep their existing numbers and avoid costly reprinting of business materials. Both 713 and 832 could now be assigned to the same geographic locations. This change made 10-digit dialing mandatory for all local calls in the Houston area.

July 1, 2014: Second Overlay – Area Code 346

On July 1, 2014, area code 346 was added as another overlay, bringing the total to four area codes serving the same region as number demand continued to grow.

January 23, 2025: Third Overlay – Area Code 621

Most recently, area code 621 was implemented on January 23, 2025, bringing the total to five area codes (713, 281, 832, 346, and 621) serving the same geographic region. The North American Numbering Plan Administrator (NANPA) – currently administered by Neustar under FCC oversight – projected the Houston area would exhaust available numbers by late 2025 without this addition.

All five area codes now serve the Houston metropolitan area as an overlay complex, meaning new numbers can be assigned with any of these area codes regardless of specific location within the region.

Where is Area Code 713? Geographic Coverage and Location

Area code 713, along with its overlay codes (281, 832, 346, and 621), serves the Houston metropolitan area across 10 counties: Harris County, Fort Bend County, Montgomery County, Chambers County, Galveston County, Brazoria County, Liberty County, San Jacinto County, Waller County, and Austin County.

Time Zone: All 713 area code phone numbers operate in the Central Time Zone (CT), which is UTC-6 during standard time and UTC-5 during daylight saving time. Houston observes daylight saving time from the second Sunday in March through the first Sunday in November.

Major cities and communities within this coverage area include:

• Houston (primary city, 2.3+ million population)
• Pasadena
• Pearland
• Sugar Land
• The Woodlands
• League City
• Missouri City
• Friendswood
• Deer Park
• Baytown
• Conroe
• Galveston
• Texas City
• Humble
• Katy
• Cypress
• Spring
• Tomball
• Richmond
• Rosenberg

10-Digit Dialing Requirement for 713 Calls

Since January 16, 1999, when area code 832 was introduced as the first overlay, all calls within the Houston metropolitan area require 10-digit dialing (area code + 7-digit number), even for local calls. According to FCC regulations, this requirement applies to all five area codes: 713, 281, 832, 346, and 621.

When you dial a local Houston number:

• Always include the area code (713, 281, 832, 346, or 621).
• Dial the full 10-digit number.
• Do not dial "1" before the area code for local calls.
• Dial "1" before the area code only for long-distance calls.

What happens if you dial incorrectly?

• If you dial only 7 digits, the call won't complete. You'll hear a recorded message instructing you to hang up and redial using 10 digits.
• Dialing "1" before the area code for a local call typically completes successfully but may result in long-distance charges depending on your carrier plan.
• If you accidentally dial an incomplete number, hang up and redial.

Impact on older systems: PBX systems, alarm systems, fax machines, and other automated dialing equipment installed before 1999 may need reprogramming to support 10-digit dialing. Verify that security systems, elevator emergency phones, and medical alert systems are configured correctly. Contact your equipment vendor or telephone service provider for assistance with updates.

Regulatory Oversight

The Public Utility Commission of Texas (PUCT), established in 1975 under the Public Utility Regulatory Act (PURA), oversees telecommunications services in Texas, including area code assignments and numbering resources in the Houston metropolitan area. The PUCT has authority to decide when and in what form to introduce new area codes within Texas boundaries.

Contact the PUCT for telecommunications issues:

• Website: puc.texas.gov
• Phone: 512-936-7000
• Toll-free: 888-782-8477
• Area Code Questions: areacode@puc.state.tx.us

Federal oversight: The Federal Communications Commission (FCC) has full jurisdiction over telephone number administration in the United States, setting policies to promote competitive markets and ensure efficient use of numbers. The North American Numbering Plan Administrator (NANPA), currently operated by Neustar, manages day-to-day number allocation, studies growth patterns, makes projections, and notifies state regulators when you need new area codes. NANPA also assigns telephone number prefixes within each area code to telecommunications carriers.

How the process works:

1. NANPA monitors number usage and projects when an area code approaches "exhaust."
2. NANPA holds meetings with telecommunications industry representatives and affected communities.
3. Stakeholders develop recommendations for the PUCT.
4. The PUCT conducts public meetings, accepts comments, and makes final decisions.
5. NANPA assigns the specific new area code number and coordinates implementation.

For Developers: Working with Houston 713 Phone Numbers

Follow these technical guidelines when building applications that handle Houston phone numbers:

Phone Number Format

Use the E.164 international format for storing and processing phone numbers:

+1713XXXXXXX

Where:

• +1 = Country code for the United States and Canada
• 713 = Area code
• XXXXXXX = 7-digit local number

Common formatting mistakes to avoid:

• Storing numbers with inconsistent formatting (parentheses, hyphens, spaces)
• Omitting the country code for "domestic only" systems (fails when internationalization is needed)
• Using area code to determine geographic location (overlays make this unreliable)
• Not accounting for toll-free numbers (800, 888, 877, 866, 855, 844, 833) which follow different rules

Validation Rules

Validate Houston-area phone numbers with these criteria:

function validateHoustonNumber(phoneNumber) {
  // Remove all non-digit characters
  const cleaned = phoneNumber.replace(/\D/g, '');

  // Check for valid length (10 digits for domestic, 11 with country code)
  if (cleaned.length !== 10 && cleaned.length !== 11) {
    return false;
  }

  // If 11 digits, verify country code is 1
  if (cleaned.length === 11 && !cleaned.startsWith('1')) {
    return false;
  }

  // Extract area code (last 10 digits if 11, otherwise full string)
  const areaCode = cleaned.slice(-10, -7);

  // Verify area code is valid for Houston
  const houstonAreaCodes = ['713', '281', '832', '346', '621'];
  if (!houstonAreaCodes.includes(areaCode)) {
    return false;
  }

  // Extract exchange code (NXX format – first digit must be 2-9)
  const exchangeCode = cleaned.slice(-7, -4);
  if (exchangeCode[0] < '2' || exchangeCode[0] > '9') {
    return false;
  }

  // Reject reserved/invalid exchange codes
  // N11 codes (211, 311, 411, 511, 611, 711, 811, 911) are invalid as exchange codes
  if (exchangeCode[1] === '1' && exchangeCode[2] === '1') {
    return false;
  }

  // 555-01XX range is reserved for fictional use (except 555-0100 to 555-0199)
  if (exchangeCode === '555') {
    const lineNumber = cleaned.slice(-4);
    const lineNum = parseInt(lineNumber, 10);
    if (lineNum >= 100 && lineNum <= 199) {
      return false; // Reserved range
    }
  }

  return true;
}

Error handling example:

function validateWithErrors(phoneNumber) {
  const cleaned = phoneNumber.replace(/\D/g_ '');

  if (cleaned.length < 10) {
    throw new Error('Phone number too short. Must be 10 digits (or 11 with country code).');
  }

  if (cleaned.length > 11) {
    throw new Error('Phone number too long. Maximum 11 digits.');
  }

  if (cleaned.length === 11 && !cleaned.startsWith('1')) {
    throw new Error('Invalid country code. Must start with 1 for US numbers.');
  }

  const areaCode = cleaned.slice(-10, -7);
  const houstonAreaCodes = ['713', '281', '832', '346', '621'];

  if (!houstonAreaCodes.includes(areaCode)) {
    throw new Error(`Area code ${areaCode} is not valid for Houston. Must be 713, 281, 832, 346, or 621.`);
  }

  const exchangeCode = cleaned.slice(-7, -4);
  if (exchangeCode[0] < '2' || exchangeCode[0] > '9') {
    throw new Error('Invalid exchange code. First digit must be 2-9.');
  }

  if (exchangeCode[1] === '1' && exchangeCode[2] === '1') {
    throw new Error(`Exchange code ${exchangeCode} is reserved for N11 service codes.`);
  }

  return cleaned.length === 11 ? cleaned : '1' + cleaned;
}

Display Format

Format phone numbers consistently for your users:

function formatPhoneNumber(phoneNumber) {
  const cleaned = phoneNumber.replace(/\D/g, '');
  const match = cleaned.match(/^1?(\d{3})(\d{3})(\d{4})$/);

  if (match) {
    return '(' + match[1] + ') ' + match[2] + '-' + match[3];
  }

  return phoneNumber;
}

// Example output: (713) 555-0123

International display format:

function formatInternational(phoneNumber) {
  const cleaned = phoneNumber.replace(/\D/g, '');
  const match = cleaned.match(/^1?(\d{3})(\d{3})(\d{4})$/);

  if (match) {
    return '+1 ' + match[1] + ' ' + match[2] + ' ' + match[3];
  }

  return phoneNumber;
}

// Example output: +1 713 555 0123

Database Storage

Store phone numbers in E.164 format in your database:

CREATE TABLE contacts (
  id SERIAL PRIMARY KEY,
  name VARCHAR(255),
  phone VARCHAR(15) CHECK (phone ~ '^\+1[2-9]\d{9}$'),
  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  INDEX idx_phone (phone)
);

Performance considerations:

• Create an index on the phone column for faster lookups.
• Consider storing a normalized version (digits only) in a separate indexed column for search operations.
• Use VARCHAR(15) to accommodate international E.164 format (max 15 digits per ITU-T recommendation).
• Add CHECK constraints to enforce format validation at the database level.

Data migration when area codes change: When new overlay codes are added (like the 621 overlay in 2025), existing phone numbers don't change – only new assignments use the new code. However, you should:

1. Update validation logic to include the new area code.
2. Update any hardcoded area code lists in your application.
3. Verify that display logic doesn't assume specific area codes indicate specific locations (overlays break geographic assumptions).
4. Test that users can successfully enter and validate numbers with the new area code.
5. Update documentation and help text to reflect the new code.

Key Takeaways

• Area code 713 has served Houston since 1947, making it one of the original NANP area codes.
• Five area codes (713, 281, 832, 346, and 621) now serve the Houston metropolitan area as overlays.
• Always use 10-digit dialing for all local calls in Houston (required since January 16, 1999).
• Coverage spans 10 counties across the Houston metropolitan area in the Central Time Zone.
• The newest overlay, area code 621, was implemented on January 23, 2025.
• Store Houston phone numbers in E.164 format (+1713XXXXXXX) for international compatibility.
• All five area codes can be assigned to any location within the coverage area.
• The FCC oversees national numbering policy, while PUCT handles Texas-specific implementation.
• NANPA administers day-to-day number allocation and projects future exhaustion dates.

Frequently Asked Questions

What area code is 713?

Area code 713 is Houston, Texas's area code. It's Houston's original and most iconic area code, established in October 1947 as part of the North American Numbering Plan. Today, 713 covers the entire Houston metropolitan area alongside overlay codes 281, 832, 346, and 621.

Do I need to dial the area code for local calls in Houston?

Yes. Since January 16, 1999, you must dial all 10 digits (area code + phone number) for all local calls in the Houston area, even when calling within the same area code. Do not dial "1" before the area code for local calls. This FCC-mandated requirement enables overlay area codes to function properly.

What's the difference between 713 and 281 area codes?

Both area codes serve the Houston metropolitan area. Originally, 713 served central Houston while 281 served suburban areas (starting November 2, 1996), but today both area codes – along with 832, 346, and 621 – serve the entire Houston region as overlays. Your location no longer determines which area code you receive.

Can I get a 713 phone number?

Availability depends on your service provider and current number inventory. While you can request a specific area code, 713 numbers have become scarce due to the area code's age and Houston's growth. Your provider may assign 281, 832, 346, or 621 instead.

Number portability: If you already have a phone number (including a 713 number), you can keep it when switching carriers thanks to local number portability (LNP) rules established by the FCC. Contact your new carrier to initiate a number port. Porting a number requires two numbers temporarily (one from the original switch, one from the new switch) for routing purposes.

Why does Houston have so many area codes?

Houston's population growth has created continuous demand for new phone numbers. Cell phones, fax machines, pagers, alarm systems, and inefficient 10,000-number block assignments accelerate number exhaustion. Rather than splitting the region into smaller geographic areas (which would require businesses to change numbers and create confusion), regulators added overlay area codes (832 in 1999, 346 in 2014, and 621 in 2025) that serve the same geographic area as 713 and 281. This approach keeps communities together while providing sufficient phone numbers.

When was area code 621 added to Houston?

Area code 621 was implemented on January 23, 2025, as the most recent overlay for the Houston metropolitan area. It serves the same geographic region as 713, 281, 832, and 346. NANPA projected the Houston area would exhaust available numbers by late 2025 without this addition.

What time zone is area code 713?

Area code 713 operates in the Central Time Zone (CT), UTC-6 during standard time and UTC-5 during daylight saving time. All Houston area codes (713, 281, 832, 346, and 621) are in the Central Time Zone, which is one hour behind Eastern Time and one hour ahead of Mountain Time.

How do I report phone number scams or robocalls in Houston?

To report unwanted calls or scam attempts:

• FCC Complaint Center: File complaints at consumercomplaints.fcc.gov or call 1-888-CALL-FCC (1-888-225-5322).
• Federal Trade Commission: Report at reportfraud.ftc.gov or call 1-877-FTC-HELP.
• National Do Not Call Registry: Register your number at donotcall.gov or call 1-888-382-1222.

Robocalls and caller ID spoofing (displaying fake Houston area codes) are common tactics. The area code alone doesn't indicate whether a call is legitimate – scammers can spoof any area code including 713, 281, 832, 346, and 621.

Will Houston need more area codes in the future?

Likely. According to NANPA's projections, Houston's continuous growth means the region may need additional overlays within the next 10-15 years. NANPA monitors number usage quarterly and alerts the PUCT when exhaust is projected within 3-4 years, allowing time for planning and implementation of new codes.

Can I send SMS/MMS messages to all Houston area codes?

Yes, you can send SMS and MMS messages to mobile phone numbers in any of Houston's area codes (713, 281, 832, 346, 621). However:

• Landline numbers cannot receive SMS/MMS regardless of area code.
• Use a phone number validation service to verify line type (mobile vs. landline) before sending.
• VoIP numbers may support SMS depending on the provider.
• Toll-free numbers (800, 888, etc.) require special configuration for SMS support.

Developer note: Implement proper error handling for failed deliveries when building SMS applications. Most SMS APIs return error codes indicating whether a number is invalid, unreachable, or a landline. Store line type information to avoid repeated attempts to send SMS to landlines.