To call a US number from another country, you need three things: your country's exit code, the US country code (1), and the person's full 10-digit phone number.
From the United Kingdom, where the exit code is 00, a call to 555-123-4567 means dialing 00-1-555-123-4567. The same formula works for any call to the States.
The US phone number format
US phone numbers aren't random. They follow a 10-digit format laid out by the North American Numbering Plan (NANP), which makes sure every number is unique, whether it belongs to a landline in a small town or a cell phone in a big city.
Like a postal address, each part of the number narrows down where the call goes.
The 10-digit structure
A US phone number has two parts. The first gets your call to the right geographic region, and the second picks out the exact phone line.
- The area code (the first 3 digits) identifies the region. 212 is famously linked to Manhattan, while 310 covers parts of Los Angeles. The code narrows the location from the whole country to one metropolitan area or region.
- The local number (the last 7 digits) belongs to one phone line within that area code. It has two parts of its own: a three-digit exchange code and a four-digit line number.
Anatomy of a US phone number
| Component | Example | Purpose |
|---|---|---|
| Area Code | (555) |
A three-digit code that specifies a geographic region within the United States. |
| Exchange Code | 123 |
The next three digits that route the call to a specific central telephone office. |
| Line Number | 4567 |
The final four digits that identify the unique subscriber line within that exchange. |
Always dial the full 10-digit number, including the area code. In many parts of the US you can no longer drop the area code for local calls, so dialing all ten digits saves failed calls.
The NANP was introduced in the 1940s. On November 10, 1951, the first direct-dialed long-distance call using an area code was made, and today's system grew from there.
Calling the US from another country
A call to the US from abroad has three parts. The first is your local exit code, a short number that tells your phone provider you're making an international call. It depends on where you are: most of Europe uses 00 and Japan uses 010. From Canada you need no exit code: dial 1 and the number, as for a call within Canada.
Next comes the US country code, which is always 1. Last, you dial the full 10-digit US number: the three-digit area code followed by the seven-digit local number.
You start with the code to get "out" of your country, then the code to get "into" the US, and finish with the person's number.
A few real-world examples
The exit code changes with your location, but the formula stays the same.
- From the UK to New York (212), dial
00(the UK exit code), then1(the US country code), then the number, such as212-555-0199. The full string is 0012125550199. - From Mexico to Los Angeles (310), dial
00(Mexico's exit code), then1for the US, then the LA number, such as310-555-0142. All together, that's 0013105550142. - From India to Chicago (312), start with India's exit code, which is also
00, then1and the Chicago number, such as312-555-0183. The complete number is 0013125550183.
The logic is the same from any country. Our +1 country code guide has more detail.
The most common mistakes are forgetting the local exit code and adding a "0" after the US country code. Keep it clean: exit code + 1 + 10-digit number.
Apps that add the codes for you
You don't always have to remember the codes. Web-based calling services like CallSky.io, which is our product, handle the international formatting for you.
Instead of typing a long string of digits, you select the United States from a country list, and the app adds the +1 country code automatically.
Then you enter the 10-digit number you want to call. It avoids misdials, which helps most when you're calling several numbers.
US area codes and local dialing
In the U.S., area codes work like zip codes for the phone network. The three-digit code routes your call to the right place, whether it comes from across the street or the other side of the world.
When the system was set up in the 1940s, the North American Numbering Plan (NANP) had only 86 area codes. The biggest cities got the codes that were quickest to dial on rotary phones, which is why New York City got 212 and Los Angeles got 213. Cell phones and VoIP lines have since pushed the total past 300 area codes, and more are added all the time.
Why 10-digit dialing is now the norm
Many areas now require 10-digit dialing, even for local calls. If you grew up dialing seven digits to call a friend in the same town, that habit is on its way out, because of "area code overlays."
An overlay adds a new area code to the same geographic area as an existing one, to provide more phone numbers. It's common in big metro areas where one code isn't enough anymore. Forgetting to dial the area code is one of the most common reasons a local call won't go through.
The safest habit is to dial all 10 digits (area code + number) wherever you are in the US, for a neighbor or a business across town. Then you don't have to know whether you're in an overlay area, and the call goes through on the first try.
US toll-free and special numbers
Not every number you come across in the U.S. fits the standard local or long-distance format. Businesses and services often use special numbers.
The most common are toll-free numbers, which start with 800, 888, 877, 866 or a few other prefixes. From within the US they are free to dial, because the company on the other end pays for the call.
Calling toll-free numbers from abroad
This trips a lot of people up: the "toll-free" part usually disappears the moment you dial from outside the United States. Your home phone provider will almost certainly treat it as a standard international call and bill you for it.
The dialing sequence stays the same: your country's exit code, the US country code (1), then the full toll-free number.
From the UK, to call 1-888-555-0101 you dial 00 + 1 + 888 + 555-0101.
Toll-free numbers date back to 1967, when AT&T introduced the original 800 prefix to make it easier for customers to reach businesses. As demand grew, more prefixes were added. Wikipedia has more on the evolution of telephone number conventions.
Never assume a US toll-free number is free to call from your country. Many can't be reached from outside North America at all, so if the call fails, look for a regular number on the company's website.
Other US service numbers
Two other numbers are worth knowing:
- 911 is for emergencies that need police, firefighters or an ambulance. It only works from within the US, and it should only be used in a genuine crisis.
- 411 is directory assistance, for looking up the number of a person or business. Most carriers charge a fee for it.
Cheaper ways to call the US
If you still call the United States over old-school phone lines, you're probably overspending.
Voice over Internet Protocol (VoIP) services and calling apps route your calls through the internet instead of traditional phone networks. With a decent internet connection, calls cost much less.
CallSky.io, our product, works this way: it uses VoIP to call any US number, landline or mobile.
VoIP vs. traditional calling
Your mobile provider probably charges steep per-minute rates for any call that crosses a border. VoIP services usually charge much less, and their pricing is easier to see up front. See USA calling rates from $0.03/min.
Our guide on how to make international calls breaks down the costs.
Getting started with a VoIP service is simple: sign up, add a little credit, and dial from your browser or an app.
Common questions about dialing US numbers
What to do if your call fails
The most common reason a call to the U.S. doesn't go through is a typo in the dialing sequence, so check that first.
Look at the number you dialed. Did you include your country's exit code? Did you include the U.S. country code, which is always 1? Is the 10-digit number correct, with no extra zeros?
If the number looks right, check your phone plan. Many mobile carriers block international calling by default to prevent unexpected charges, and a quick call to your provider will tell you whether your plan allows international calls.
A failed call almost always comes down to a dialing error, a block on your phone plan, or, if you're using a VoIP app, a spotty internet connection.
Extensions and other common questions
- To reach an extension, dial the main 10-digit number. Once you're connected, wait for the greeting and the prompt, then key in the extension.
- In the U.S., mobile numbers and landlines are dialed the same way. Both use the same 10-digit format, with no special prefix.
- A VoIP or Wi-Fi calling app needs a stable internet connection, and a weak signal causes dropped calls and poor quality. Our guide to the best app for Wi-Fi calling has more.
CallSky is our product. Our rates to the USA start at $0.03/min.