A flat recorded voice tells you the call cannot be completed as dialed, and then it goes quiet, as if you ought to know what you did. Anyone who has stood in a hallway holding a landline receiver after that message has asked the same thing: did I need a 1 at the front, or did I put one there that I should not have? I put off writing this page because the honest answer to "do I need the 1?" is "it depends on the phone in your hand", and that is a poor headline. It is also the true one, and the reasons behind it are more interesting than the rule.
Start with what the 1 was for. In the North American plan, a ten-digit number is a complete address: area code, exchange, line. For a long time the local switch could not tell by looking at the first digits whether you meant a neighbour three streets away or a cousin two states over, so callers were taught to dial a 1 first whenever the call left the local calling area. The 1 was a signal to the switch, not a piece of the number. It said, in effect, "what follows is a full ten digits, and please route it beyond town." Seven digits meant local, and 1 plus ten meant not local. Whole generations learned it as a rhythm and never thought about it again.
What the 1 is, and what it is not
The technical name is a trunk prefix. The word trunk comes from the long-distance lines that carry calls between switching centres, and the prefix is the domestic instruction to use one. Many countries have a version of it. In the United Kingdom and Germany it is a 0 that gets dialed before the area code for calls between regions. In the North American plan it happens to be 1, which is where the confusion begins, because 1 is also the country code of the whole plan.
Two different jobs share one digit. The country code is for the world: when you call from another country, or when a phone shows a number in its full international form, the 1 appears right after the plus. The dialed 1 is for the continent's own network and exists only for callers inside it. A number that shows on your screen as +1 followed by ten digits is carrying the country code, and the phone adds whatever your network needs when you call back. That is why people who save contacts as plus, 1 and ten digits seldom have trouble. It is also why a contact saved as +1 1 212 555 0100, with both a plus and a stray dialed 1, fails: the network is told the country twice. I made a point of explaining the plus in why numbers start with +1, because nearly every tangle in this area comes from treating the two ones as the same thing.
The dialed 1 also has nothing to do with leaving the country. People who learned to dial 1 for long distance sometimes assume it is the exit code for international calls, and it is not. From the United States and Canada the exit code is 011, and a number to Europe starts 011 and a country code, never 1 and then 011. If you ever find yourself dialing a 1 in front of an international number, stop and take it off. The reverse trap exists as well. A caller abroad who wants to reach a US number must include the 1, but as the country code, right after the exit code or plus sign. I have tried to untangle that from the other side in dialing the US from abroad.
One last sighting of the 1 deserves a mention, because it causes needless worry. When a missed call appears on your screen as +1 followed by ten digits, the 1 is only the country code in the standard display, and it says nothing unusual about the caller. You do not have to add or remove anything to call back, since the phone handles the format. Whether you should call back at all is a different question, and one for the area code and your own judgment, not for the leading digit.
How overlays and a three-digit code changed the rules
For most of the plan's history the arrangement was easy to remember: seven digits for local calls, 1 plus ten for everything else. Two developments broke it.
The first is the overlay. When a region runs short of numbers, regulators have two choices. They can split the map and give half the territory a new area code, which forces some people to change their numbers, or they can add a second area code over the same geography, which does not. Overlays have become the common choice because nobody has to give up a number. The price is that a neighbour might now have a different area code from yours, so the old shortcut of leaving the area code off no longer works. In an overlay region every call, even next door, needs all ten digits. The recording you hear when you dial seven digits there is the system following a rule from the regulator and the carrier. It is not a glitch, and trying again with seven digits will not help. Whether the call then also wants a 1 in front is a matter for the carrier and the kind of phone, and the next section is about exactly that.
The second development is newer, and it concerns the short three-digit codes that people dial in a crisis. When 988 was introduced as a three-digit number, some areas found that seven-digit local numbers beginning with the same three digits could collide with it, and dialing rules were tightened in a number of places. I will not claim to know the rule for any particular region, because it varies and it has been changing. What matters here is the effect: more of the country now dials ten digits for every call, and fewer people can lean on the old habit of seven. The FCC's consumer pages and the numbering plan administrator at nationalnanpa.com are where the current rules live, and I reread them before I date any page that touches on them.
Put the two changes together and you get the situation most people are in today. Local calling is often ten digits whether you like it or not, and 1 plus ten is the older way to mark a call as leaving town. Which of those two your phone insists on is where mobile phones, landlines and office systems part company.
Phones that follow their own rules
A mobile phone is the forgiving one. It does not guess at a route from the first digits of what you typed. It sends the whole number to the network, and the network works out where it goes. So ten digits connect, and 1 plus ten digits connect too, and for practical purposes the difference is cosmetic. Seven digits, on the other hand, often fail on a mobile, because the phone has no way of knowing which area code you meant. Some carriers fill in your own, and many do not. If you carry a phone from one region to another, the contacts you saved with only seven digits at home are the ones that will let you down away from it. Nothing is wrong with the phone. The number was never complete.
A landline is where the local rules bite. On an old-style line in a region that still allows seven-digit local dialing, a local call is seven digits and anything outside your area code is 1 plus ten. In an overlay region, local calls need ten digits and many landlines still want a 1 for calls outside the area code. The telephone company's recordings are the only help you get, and they are more informative than they sound. A message telling you to hang up and dial 1 first means what it says. A message telling you to include the area code means you gave too few digits. If the call connects, you have found the format your line wants, and it is worth remembering rather than rediscovering next week.
Then there are phones that do not belong to the public network in the plain sense: office systems and hotel rooms. A business phone system, a PBX, often wants a digit for an outside line before any outgoing number, commonly 8 or 9, and after that its own configuration decides whether it needs the 1 and ten digits. Hotels work the same way and often add a per-call fee for the privilege. The system will tell you its rules with a fast busy signal or a short announcement, and I have learned to listen to the announcement all the way through, because it is usually the whole manual. When the call fails from such a phone, the sensible move is to ask the front desk or the office administrator, not to experiment with digits at random.
Money, toll-free numbers and a way to test
Does the extra 1 change what a call costs? On its own, no. The charge depends on your plan and on the destination, not on a digit. Plans today very often treat every call within the United States alike. Where the digit still matters is on older landline plans with a defined local calling area, where dialing 1 marks a call as long distance and the carrier bills it that way. If you are unsure which kind of plan you have, the plan's page or a recent bill answers it faster than any guess of mine. The real money surprise lies elsewhere. Calls to Canada and to a number of Caribbean countries also use 1 plus ten digits and look entirely domestic. The prefix is the same and the billing may not be, and I gave that its own page, calling Canada and the Caribbean from the US, because it is the source of most avoidable phone bill shocks I hear about.
Toll-free numbers sit a little to one side of all this. The codes 800, 833, 844, 855, 866, 877 and 888 are dialed with the 1 in front, and they are free to the caller, who therefore tends to relax. They have no home city, so a caller who shows up as 1-800-something may be a bank, a pharmacy or a spoofer, and the digits give you no location to check. Our prefix reader will at least confirm that a code is toll-free, which is a fact about the line and not a certificate of the company behind it.
So how do you find out what your own phone wants? I use a test that takes under a minute and never involves guessing. Dial the number as ten digits with no 1 and listen. If a recording tells you to hang up and dial 1 first, redial with the 1 and make a note of it for that phone. If the recording tells you to include the area code, you gave too few digits, and you redial with all ten. If it connects, you are done, and that is the format the phone and the plan accept. The recordings differ in wording from carrier to carrier but never in meaning, and the one thing worth avoiding is adding and removing digits at random until something works, because that is how a wrong number gets dialed.
If I had to give one rule for people who dislike tests, it would be this. On a mobile, dial all ten digits and stop thinking about the 1. On a landline or an office system, dial 1 plus ten for anything outside your own area code, and read the recording if it turns you away. And when you save a contact for any phone you may carry abroad, give it the plus form, the 1 included as the country code, with nothing extra in front. The whole procedure for that is in saving contacts in international format. Keep the two ones apart in your head and the hallway recording will rarely need to speak to you again.
Next in the bookDialing internationally from the US: a glossary from 011 to the plus sign