Communication matters for both businesses and individuals, so understanding the parts of a phone number and variations is important. Every country has its unique country phone code. For the USA, it is “+1.” Telephone numbers in the USA follow a standard 10-digit format, which is made up of three parts: area code, exchange code, and line number, written as (XXX) XXX - XXXX. When you dial from outside the US, you need to add the country code +1 at the beginning of the phone number: +1 (XXX) XXX-XXXX.
In this blog, we will explore the US phone number format along with a few examples. It will help you understand what each part signifies.
TL;DR
- The US phone number format is a standardized 10-digit numbering structure that is used across the US under the NANP (North American Numbering Plan).
- The parts of a US phone number are the country code, area code, exchange code, and line number.
- The last three parts form a 10-digit number.
- For example: +1 (212) 555-XXX7. Here +1 is the country code, 212 is the area code, 555 is the exchange code, and XXX7 is the line number.
What are the Parts of a Phone Number in the US?
A US phone number typically has four parts:
- Country Code
- Area Code
- Exchange Code
- Line Number
The last three of them make a 10-digit number. When you dial from outside the US, you need to add the country code +1 at the beginning of the number.
Let’s understand it through a US phone number example.
Take +1 (610) 234-7XXX. Let’s understand each part of this phone number.
| Part | Digits | Example | What it does |
| Country code | 1 | +1 | Shows the number belongs to the US, Canada, or a Caribbean country on the same plan. |
| Area code | 3 | 614 | Points to a region |
| Exchange code | 3 | 234 | Also called the prefix or central office code |
| Line number | 4 | 7XXX | Identifies one specific line |
While writing a number in the international format, you need to add the country code.
Let’s Understand Each Part in Detail
Let’s look at each part of a phone number.
1. Country Code
The first part is the country code. For the US, it is +1, and Canada and most Caribbean nations on the NANP plan also share the same country code.
2. Area Code (3 digits)
The area code is the first three digits of the 10-digit phone number. It points to the specific region, and its first digit is always 2 through 9. The second and third digits can be 0-9. An area code also shows where a number originated. Many people keep their number after they move.
3. Exchange Code (3 digits)
The exchange code is the next three digits, which is also called the prefix or the central office code. It follows the same rule as the area code: the first digit is 2 through 9, and the second and third digits can be anything from 0 to 9.
4. Line Number (4 digits)
The line number is the last four digits, and it can be anything from 0000 to 9999. It identifies one specific line within the exchange. It is also known as the subscriber number.
US Phone Number Format: Different Types and Styles to Write It
Generally, US phone numbers come in four main types:
- Landline
- Mobile
- Toll-free
- Virtual
All follow the same 10-digit (XXX) XXX-XXXX format but serve different purposes.
| Type | Example | Description |
| Landline | +1 (212) 457-XXX0 | Residential or office line tied to a physical location. |
| Mobile | +1 (512) XXX-4523 | Personal or business mobile number that is portable across devices. |
| Toll-Free | +1 (877) 542-X3XX | Customer service numbers, free for callers within the US. |
| Virtual | +1 (424) 3XX-7XX0 | Internet-based numbers that are not tied to a physical device. |
You will see the 5 most common styles for phone number formats in the USA.
Let’s understand them one by one.
| Style | Example | Best used for |
| (XXX) XXX-XXXX | (610) 234-7XXX | Websites, flyers, business cards |
| XXX-XXX-XXXX | 610-234-7XXX | Forms and everyday writing |
| XXX.XXX .XXXX | 610.234.7XXX | Design-heavy layouts |
| +1 XXX XXX XXXX | +1 610 234 7XXX | Materials for a global audience |
| +1XXXXXXXXXX (E.164) | +16102347XXX | Databases, CRMs, texting and calling tools |
You should choose one style and stick to it. We advise using the E.164 style because it is the preferred way to store numbers in databases and pass them between systems.
What is the E.164 Format of a US Phone Number?
The E.164 format is the international standard maintained by the ITU (International Telecommunication Union). It defines a single canonical format that every modern phone system internally uses.
For example:
+16102347XXX - A plus sign, the country code, and then the national number with no spaces or punctuation.
It is important to follow the E.164 format because every telecom platform, CRM, or VoIP provider stores numbers in this format. If you don’t store numbers in this format, you need to write conversion logic to handle (610) 234-7XXX vs. 610.234.7XXX vs. 1-610-234-7XXX.
So, choose the standard E.164 format.
How to Find the Area Code of a Specific City in the US
Area codes in the US were introduced in 1947 with the aim of organizing phone numbers geographically across the country. If you want to find the area code of a particular city in the USA, you can visit the official website of the Federal Communications Commission (FCC). On this website, the area code associated with the city is listed. Remember that no two cities in the US share the same area code.
We have listed below some of the area codes in the US.
Southern US Area Codes
The Southern region has the following area codes.
| State | Area Code |
| Alabama | 205, 251, 256, 334, 938 |
| Arkansas | 479, 501, 870 |
| Delaware | 302 |
| Florida | 305, 321, 352, 407, 561, 727, 813, 850, 904 |
| Georgia | 229, 404, 470, 478, 678, 706, 770, 912 |
| Kentucky | 270, 364, 502, 606, 859 |
| Louisiana | 225, 318, 337, 504, 985 |
| Maryland | 240, 301, 410, 443, 667 |
| Mississippi | 228, 601, 662, 769 |
| North Carolina | 252, 336, 704, 828, 910, 919, 980 |
| Oklahoma | 405, 539, 580, 918 |
| South Carolina | 803, 843, 864 |
| Tennessee | 423, 615, 731, 865, 901, 931 |
| Texas | 210, 214, 281, 512, 713, 817, 972 |
| Virginia | 276, 434, 540, 571, 703, 757, 804 |
| West Virginia | 304, 681 |
Midwestern US Area Codes
This is the industrial and agricultural core of the United States. Here are a few area codes for the Midwestern US.
| States | Major Area Codes |
| Illinois | 217, 309, 312, 618, 630, 708, 773, 815, 847 |
| Indiana | 219, 260, 317, 463, 574, 765, 812, 930 |
| Iowa | 319, 515, 563, 641, 712 |
| Kansas | 316, 620, 785, 913 |
| Michigan | 231, 248, 269, 313, 517, 586, 616, 734, 810, 906 |
| Michigan (Upper Peninsula) | 906 |
| Minnesota | 218, 320, 507, 612, 651, 763, 952 |
| Missouri | 314, 417, 573, 636, 660, 816 |
| Nebraska | 308, 402, 531 |
| North Dakota | 701 |
| Ohio | 216, 234, 330, 419, 440, 513, 567, 614, 740, 937 |
| South Dakota | 605 |
| Wisconsin | 262, 414, 534, 608, 715, 920 |
Western US Area Codes
The western part of the US includes high-population centers and remote regions.
| State | Major Area Codes |
| Alaska | 907 |
| Arizona | 480, 520, 602, 623, 928 |
| California | 209, 213, 310, 323, 408, 415, 424, 510, 559, 619, 626, 650, 707, 714, 760, 805, 818, 831, 858, 909, 916, 925, 949, 951 |
| Colorado | 303, 719, 720, 970 |
| Hawaii | 808 |
| Idaho | 208, 986 |
| Montana | 406 |
| Nevada | 702, 725, 775 |
| New Mexico | 505, 575 |
| Oregon | 458, 503, 541, 971 |
| Utah | 385, 435, 801 |
| Washington | 206, 253, 360, 425, 509 |
| Wyoming | 307 |
Northeastern US Area Codes
Northeast has the oldest and most densely populated areas in the US.
| State | Area Codes |
| Connecticut | 203, 475, 860, 959 |
| Maine | 207 |
| Massachusetts | 339, 351, 413, 508, 617, 774, 781, 857, 978 |
| New Hampshire | 603 |
| New Jersey | 201, 551, 609, 732, 848, 856, 862, 908, 973 |
| New York | 212, 315, 332, 347, 516, 518, 585, 607, 631, 646, 716, 718, 845, 914, 917, 929, 934 |
| Pennsylvania | 215, 267, 272, 412, 484, 570, 610, 717, 724, 814, 878 |
| Rhode Island | 401 |
| Vermont | 802 |
What Makes a Phone Number Format Valid
A valid US phone number follows these basic rules.
- It has 10 digits: the area code, exchange code, and line number.
- The area code and exchange code start with 2 through 9.
- Service codes are off limits. Codes like 411 and 911 are reserved for services.
- Store digits only. Skip letters and extra symbols in system fields.
The issue here is that the valid format only checks structure but does not tell you if a number is active. It does not tell you if the line is a mobile or a landline.
For example:
Our number (610) 234-7XXX passes the format test, but it is a fictional number.
Common Phone Number Formatting Mistakes
You should watch for these common phone number formatting mistakes.
| Mistake | Fix |
| You skip the area code. | Always save all 10 digits. |
| Adding an extra 1 or 0. | The 1 is a dialing prefix. Save +1 once and then the 10-digit number. |
| Mixing styles in one list. | Choose one style and apply it everywhere. (Pick E.164 format) |
| Adding spaces or symbols in system fields. | E.164 numbers have no spaces, dashes, parentheses, or dots, so remove them before you save the number. |
Final Thoughts
A US phone number consists of a country code, area code, exchange code, and line number. Learn these parts of a phone number, pick one US phone number format, and your forms, contact lists, and CRM stay clean.
But a clean phone number format only solves half the problem. It does not tell you the line type of the number. Landlines can’t receive regular text messages. So when you text those numbers, messages go nowhere.
But worry not! Landline Remover helps fix this. It checks the line type of each number: mobile or landline. You get a list sorted by line type before you send your next text campaign or start dialing.
Book a demo and see which numbers in your contact list are mobile and which are landlines.