What Is a Valid US Phone Number Format?

valid us phone number

Making a phone call to the US is relatively easy, but it’s important to know the correct area code. There are currently 335 area codes in the US, including 18 non-geographic area codes and 317 geographic area codes. Area codes began to be assigned in the 1940s to make it easier for calls to be connected to the right geographic area.

New area codes are given out when one particular area gains too many phone numbers. For instance, the Metro Detroit area in Michigan had only one area code — 313 — until 1997. At that time, it was split into two area codes, 313 and 734, to accommodate the growing number of phone lines.   

Different Types of Phone Numbers

There are several different types of phone numbers, including:

  • Local landline numbers
  • Mobile numbers
  • Toll-free numbers
  • 10-digit long codes
  • Short code numbers

Landline Numbers

Opting for a local landline number is a fantastic way for businesses to show that they’re located nearby. Customers will instantly recognize the geographic area, which will help with familiarity and foster trust. After all, anyone who has the same area code has aligned themselves with the local community. It will also be easier for customers to remember your phone number, as they won’t have to memorize your area code.

Aside from using local landline numbers for home usage, they can also be utilized by:

  • Small Businesses: Having a local number will make you seem more accessible and trustworthy to customers in your area.
  • Restaurants: Using a local number helps create a sense of community and will also help encourage local diners to call your business.
  • Real Estate Agencies: Your local number will make potential clients more comfortable reaching out. They’ll know that you’re in the area, which means you should have a better understanding of their needs.

Mobile Phone Numbers

Mobile phone numbers are much more likely to be based on the area you were in when one was assigned to you. This is the reason that you almost certainly have friends or family members who live locally but do not have a local mobile number. Instead, your mobile number will travel with you, regardless of whether you’ve physically relocated. This can become complicated if you try to utilize your existing mobile number for business purposes.

Let’s say you live and work in Atlanta, GA, but you purchased your mobile phone when you lived in Florida. Unless you take the necessary steps to get your phone number changed, you’ll be asking Atlanta residents to call a Florida number to speak to you in Atlanta. This can confuse your customers, which can make it more difficult for your business to succeed.

Toll-Free Numbers

Toll-free numbers are identified by the 800, 888, 877, 866, 855, 844, and 833 prefixes. These numbers allow callers to reach businesses or individuals without incurring charges for the call.

10-Digit Long Codes

In the US, 10-digit long codes are regular phone numbers, whether landline or mobile, that include the area code followed by the subscriber number. This format is used for both local and long-distance calls within the country.

Short Code Numbers

Short code numbers are typically five or six digits long and are used for SMS communications and other purposes. They are often used for marketing campaigns, charitable donations, and mobile services. Short code numbers can be more costly than using a 10-digit long code, mobile number, or local landline number, particularly for businesses or organizations that send a large volume of messages.

Format of a Valid US Phone Number

phone number format us

A valid US phone number has certain formatting requirements, regardless of which type of phone number you have.

Number of Digits in a Phone Number in the US

If you’re calling from within the US, there will be a total of 10 digits required. Anyone calling the US from outside of the country, however, will have to add an 11th number. Each number can be further broken down to help you understand where you’ll be calling.

Three-Digit Area Code

The three-digit area code is placed at the beginning of the number. Its purpose is to define the broader geographic region where the phone number resides. Unfortunately, area codes do not go in any type of numerical sequence. Therefore, you won’t find 313 next to 314, for instance. Instead, area codes were assigned based on where the densest areas of population were located.

Central Office Code

The next three digits refer to a smaller geographic area that’s set within the broader area. In other words, when you dial the area code, you’ll be within the county. Once you dial the next three numbers, they will narrow it down to the city.

Please note: Not all area codes are confined to one county, just as not all central office calling codes are limited to one city. For the purposes of this article, however, this is the easiest way to explain how these numbers work.

Subscriber Number

Finally, we’ve come to the last four digits of your phone number. These provide 10,000 different combinations, although your service provider may not have access to all of them. Instead, they’ll be divided up among different providers.

Landline Phone Number Format

Landline phone numbers have the most basic format because the area code will tell you what geographic area you’re calling. It’s not possible to live in California and have a landline with a New Jersey area code, for instance.

Standard Format

The standard format for a landline number consists of the area code, central office code, and subscriber number. They look like this: (XXX) XXX-XXXX.

International Format

If someone calls you from outside of the United States and Canada, they’ll have to use the North American numbering plan. The good news is that it’s extremely simple. Simply dial a 1 before the rest of the number, like this: +1 XXX XXX XXXX.

Common Variations

Some landline numbers in the US do not require you to use 10 digits. These common variations include:

  • 211 – Community referral
  • 311 – Non-emergency police or government
  • 411 – Directory assistance
  • 511 – Travel info
  • 611 – Often used as a repair line by phone service providers
  • 711 – Relay services for the hearing impaired
  • 811 – Call before you dig the number
  • 911 – Emergency services
  • 988 – National suicide and mental health number

Mobile Phone Number Format

Mobile phone numbers look the same as landline phone numbers. The difference is that when you call a mobile number, the person may not be located where you’d think.

Standard Format

A mobile phone’s format looks like this: (XXX) XXX-XXXX. Once again, this indicates the area code, central office number, and subscriber number. The main difference between a landline and a mobile number is that the user could be located anywhere, rather than in a specific geographic area.

International Format

Just like with a landline number, you only have to add a +1 at the beginning if you’re outside of the US, so they look like this: +1 XXX XXX XXXX.

Common Variations

Mobile phone numbers have the same common variations as landline phone numbers. In other words, depending on your area, you may be able to call 211, 311, etc. as listed above.

Valid US Phone Number Examples

We’ll use a common fake number to show you how to format your calls:

Landline Number Examples

An example of a landline number is (555) 555-5555. If this were a real number, (555) would be the broad geographic location, 555 would narrow down the location, and the final 5555 would indicate the subscriber.

Mobile Number Examples

Once again, we’ll use (555) 555-5555. The primary difference is that someone with this number could live anywhere.

International Phone Numbers

example of us phone number

Making an international call requires you to know more information, which we’ll list below.

International Access Code

Before the country code, area code, etc., you must dial 011 for international calls.

Country Codes

International calls require you to provide the country code. For instance, if you wish to call Greece, you must enter 011 30 at the start of the number. Calling Iceland requires 011 354 at the beginning. The USA country code is +1. Every country on earth has a specific country code that’s one to three numbers, so be sure to look up which country codes you need to use.

Country-Specific Formats

Other countries can have their own specific formats for dialing a telephone number. A good example is the U.K., where an in-country call looks like “07911 123456” and an international call looks like “+44 7911 123456.” The country code +44 is used, and the first zero is omitted.

Dialing US Phone Numbers

You used to be able to not dial the area code if you were located in the same area. However, it’s now necessary to use the area code whenever you make a call.

Local Calls

As mentioned above, you must dial the entire local phone number, including the area code, to make a local call. Even if you live next door!

Long-Distance Calls

Long-distance calls that are within the country are generally free on mobile phones, as most mobile phone plans in the US include unlimited nationwide calling. But if your payment is past due or you have a restrictive mobile phone plan, you may not be able to make a long-distance call. Landline phones may charge extra to connect to someone outside of your local geographic region. Either way, you’ll dial 10 numbers.

Additional Considerations for Phone Numbers

Using a consistent format will make it easier to contact others. Whether you choose to write phone numbers as (555) 555-5555, 555 555-5555, or 555.555.5555, be sure you’re always consistent.

Validating Phone Numbers

Want to make sure you’ve been given a valid phone number? You can use online phone validation services, such as IPQualityScore, to check if a phone number is active and in service. These services can also identify the carrier and line type. Another option is to run a reverse phone number search to find out more information about the phone number and its owner.

Phone Number Display on Business Cards

You can use a variety of different formatting options, but it’s best to stick with (555) 555-5555. If you have an international company, you’ll want to write +1 555 555-5555.


How do you write a valid US phone number?

A valid US phone number looks like this: (555) 555-5555. This contains the geographic region: (555), central office number: 555, and the subscriber number: 5555.

How many digits does the USA phone number have?

A typical USA phone number has 10 digits and is formatted like: (555) 555-5555. If you’re calling the USA from outside of the country, it will look like: +1 (555) 555-5555.

What is a 7-digit phone number in the US?

The US 7-digit phone number does not contain the area code. In other words, it looks like 555-5555. Using the 7-digit phone number is an outdated practice. Nowadays, they’re always formatted like: (555) 555-5555.

What does a valid format for a phone number mean?

In the US, a valid format for a landline or mobile phone number will always contain 10 digits. It will look like: (555) 555-5555. The one exception is if you want to call a landline or mobile phone number in the US from outside of the country. Then, you must add +1 like: +1 (555) 555-5555.

Is the USA country code 001?

The proper format for calling a landline or mobile phone from outside the USA is +1 (555) 555-5555. The +1 can be replaced with 001. However, remembering one digit is much easier than three digits.

Eugene Kirdzei
Eugene Kirdzei

Chief Technical Officer at Nuwber
With nearly two decades of experience in the IT industry, Eugene possesses comprehensive knowledge across his professional field, including in data management, data protection, and information search. Through his writing, he aims to provide valuable insights and practical advice on how to safely explore the online environment and leverage digital tools to enhance people’s lives.