Calling the United States from the UK takes three parts: the UK's international prefix (00), the US country code (1) and the ten-digit US number. Get one of them wrong and the call fails with a recorded message, or worse, connects to a number in the UK. This guide shows the exact digits for a landline and a mobile, a worked example, what to do about US 800 numbers, and when to call so someone is actually at their desk.
The short answer
- From a UK landline: Dial 00 1, then the three-digit US area code and the seven-digit number. Example: 00 1 512 555 0142.
- From a mobile: Dial +1, then the area code and number: +1 512 555 0142. On most phones you get the plus sign by pressing and holding 0. The plus works from any country, so it's the safest way to save US numbers in your contacts.
- What not to dial: Don't add a 0 before the US area code, and don't drop the 1. US numbers have no trunk 0 like UK numbers do.
Those codes come from the ITU dialling procedures list: the UK's international prefix is 00, and the United States uses country code 1 with ten-digit national numbers. The US shares country code 1 with Canada and the other members of the North American Numbering Plan, 20 countries in all according to NANPA.
How a US phone number is built
Every US number has ten digits, usually written as (512) 555-0142 or 512-555-0142.
| Part | Example | What it is |
|---|---|---|
| Area code | 512 | Three digits for the region (512 is Austin, Texas). It never starts with 0 or 1. |
| Exchange | 555 | Three digits. It never starts with 0 or 1 either. |
| Line number | 0142 | Four digits. |
Because there's no leading 0, you write a US number in international format by putting +1 in front of all ten digits: +1 512 555 0142. If a US business gives you a number with a 1 already in front, like 1-512-555-0142, that 1 is the country code, so you dial 00 then the whole thing.
Step by step: calling from a UK landline
- Find the full ten-digit US number, including the area code.
- Dial 00 to leave the UK network.
- Dial 1 for the United States.
- Dial the area code, then the seven-digit number.
- Wait a few seconds. International calls can take a moment longer to connect.
Worked example: a customer in Leeds wants to reach a shop in Austin whose number is (512) 555-0142. From the landline they dial 00 1 512 555 0142. From a mobile they dial +1 512 555 0142.
Step by step: calling from a UK mobile
- Open the keypad and press and hold 0 until + appears.
- Type 1, then the ten-digit number with no spaces needed.
- Press call. If you save the contact as +1 512 555 0142, it works the same when you travel.
Check your plan before you dial. Calls to the US are usually charged as international calls unless your plan includes them, and the rate varies by network and plan. Your network's price guide lists the per-minute rate and any international add-ons.
Calling apps and Wi-Fi
If the person you're calling uses WhatsApp, FaceTime or another calling app, an app-to-app call over Wi-Fi or mobile data avoids international call charges, though it uses data. Some apps also call ordinary US phone numbers for a per-minute fee. In every case, you still enter the number as +1 and ten digits.
US toll-free numbers (800, 888 and others)
US toll-free numbers start with 800, 833, 844, 855, 866, 877 or 888, according to the FCC. "Toll-free" means the business pays for calls from inside the US. From the UK it's different:
- The call may not connect: Some businesses accept international calls to their toll-free numbers and some block them to avoid the cost, as Aircall's help center explains. A blocked call usually ends with a message that it can't be completed as dialed.
- It isn't free for you: If it does connect, your network may charge you for an international call.
- Look for a regular number: Many US companies list a separate "calling from outside the US" number on their contact page. Use that, or use their website chat or email.
Time difference between the UK and the US
The US spans several time zones, and both countries change their clocks, but on different dates. US daylight saving time runs from the second Sunday in March to the first Sunday in November (NIST). UK clocks go forward on the last Sunday in March and back on the last Sunday in October (GOV.UK). For a few weeks each year the gap shrinks by an hour.
| Period in 2026 | London vs New York (Eastern) | London vs Chicago (Central) | London vs Los Angeles (Pacific) |
|---|---|---|---|
| Jan 1 to Mar 7 | 5 hours ahead | 6 hours ahead | 8 hours ahead |
| Mar 8 to Mar 28 | 4 hours ahead | 5 hours ahead | 7 hours ahead |
| Mar 29 to Oct 24 | 5 hours ahead | 6 hours ahead | 8 hours ahead |
| Oct 25 to Oct 31 | 4 hours ahead | 5 hours ahead | 7 hours ahead |
| Nov 1 to Dec 31 | 5 hours ahead | 6 hours ahead | 8 hours ahead |
In practice: 2 p.m. in London is 9 a.m. in New York and 6 a.m. in Los Angeles most of the year. The best window to reach a US office is the UK afternoon, roughly 2 p.m. to 6 p.m. for the East Coast and 5 p.m. to 8 p.m. for the West Coast.
If the call won't go through
- Count the digits after the 1. There should be exactly ten.
- Remove any 0 you added in front of the area code.
- If it's a toll-free number, find the company's regular number or try chat.
- If you're on a work phone, ask whether international calls are barred on your line.
- Try +1 from a mobile. It skips the landline prefix entirely.
If your business takes calls from the UK
If you're a US store with UK customers, put your number on your site in international format (+1 512 555 0142), not only as 1-800 or (512) 555-0142. If your main number is toll-free, give overseas customers a second way in, such as website chat or email, because some toll-free numbers can't be reached from abroad. And remember that UK customers call during your early morning.
How Chargezen helps
Chargezen doesn't sell international calling or UK numbers. What it does is answer the calls and messages that reach your US business number, even at 6 a.m. Pacific when your UK customers are calling:
- Concierge answers your US number: Concierge is Chargezen's team of digital employees. On the phone it works as an AI receptionist that answers calls on your US business number at any hour, knows the caller from their number and can look up their orders. See the phone channel.
- Teammates join from anywhere: When a caller needs a person, Concierge alerts your team in the Finn app and the browser, and emails or texts the teammates you pick. A teammate can listen in and join the live call from Finn or the browser; transfers happen in the Finn app. See phone calls.
- One thread per customer: Calls, texts, website chat and email from the same customer land in one conversation, so whoever picks it up next sees what already happened. See every channel.
- US numbers only: Chargezen offers US (+1) numbers: a new toll-free number, or the US number you already have. It doesn't sell numbers in other countries, and it doesn't forward calls.
Concierge also answers website chat and email, which is useful for overseas customers who can't reach a toll-free number. Concierge Starter is $20 a month with 20,000 credits. Pro is $199 a month with 199,000 credits, or $1,990 a year. Phone and text charges are billed as used. See pricing.
Related terms: toll-free number, VoIP and AI receptionist. Related guides: how to get a US phone number in the UK, how to call the US from Canada and how to get a business phone number. See also how to call the UK from the US.
Frequently asked questions
Is it 001 or 00 1 to call the US from the UK?
It's the same thing. 00 is the UK's international prefix and 1 is the US country code, so you dial 0, 0, 1 and then the ten-digit number.
Do I need to dial the 1 if I use +?
Yes. The plus replaces 00 only. +1 512 555 0142 is right; +512 555 0142 dials a different country.
Can I call a US 1-800 number from the UK?
Sometimes. It depends on whether the business accepts international calls on that number. If it doesn't connect, use the company's regular number or online contact options.
What time is it in the US right now compared with the UK?
Most of the year New York is 5 hours behind London and Los Angeles is 8 hours behind. For about three weeks in March and one week in late October/early November, each gap is an hour shorter.
Sources
ITU dialling procedures list (international prefixes and number lengths); NANPA (country code 1, ten-digit numbers); FCC (toll-free codes); Aircall's help center (toll-free calls from abroad); NIST and GOV.UK (clock changes). All checked October 18, 2026.
