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Formula
From the UK: 00 (or +) → 1 → 10-digit NANP number (NPA-NXX-XXXX).
| Type | Domestic in US | Save as (portable) | Dial from UK |
|---|---|---|---|
| Landline (New York) | (212) 555-01XX | +1 212 555 01XX | 00 1 212 555 01XX |
| Mobile-style (D.C.) | (202) 555-01XX | +1 202 555 01XX | 00 1 202 555 01XX |
X characters are placeholders, not a private callable number. Save +1 in contacts; use 00 only for all-digit UK access. Do not store 00 in the contact.
Dial it step by step
- 1
Exit the UK network. On a mobile or modern contact book, start with +. On a UK landline, PBX, or digit-only service, dial 00.
- 2
Add the shared NANP country calling code: 1.
- 3
Add the full 10-digit national number: three-digit area code plus seven digits. There is no separate US trunk 0 to remove, and no extra 1 follows country code 1.
Portable contact format: + 1 + 10-digit NANP
Digits-only call from UK: 00 + 1 + 10-digit NANP
Mobile and landline rules
- No trunk zero: a domestic (212)… number becomes +1 212….
- Do not double the 1: international format is +1 followed by the 10 digits, not +1 1….
- +1 is shared across the North American Numbering Plan; the three-digit area code identifies the numbering-plan area.
See the United States calling-code reference and the international dialing format guide.
Worked examples
Domestic → portable international → digits-only from United Kingdom. All subscriber digits shown as X are placeholders.
| Type | Domestic in US | Save as (portable) | Dial from UK |
|---|---|---|---|
| New York landline | (212) 555-01XX | +1 212 555 01XX | 00 1 212 555 01XX |
| Los Angeles landline | (310) 555-01XX | +1 310 555 01XX | 00 1 310 555 01XX |
| Chicago landline | (312) 555-01XX | +1 312 555 01XX | 00 1 312 555 01XX |
| Washington, D.C. mobile-style | (202) 555-01XX | +1 202 555 01XX | 00 1 202 555 01XX |
Common mistakes on this route
- Dropping the three-digit area code. Dial all 10 digits after +1 or 00 1.
- Doubling the country-code 1 and producing 00 1 1 212….
- Saving 00 in the contact instead of the portable +1 format.
- Assuming +1 means the United States only; it is shared by the NANP.
Quick US area codes (from the UK)
| City / area | Area code (NPA) | After +1 / 00 1 |
|---|---|---|
| New York (Manhattan) | 212 | 212 + 7 digits |
| Los Angeles | 310 | 310 + 7 digits |
| Chicago | 312 | 312 + 7 digits |
| Washington, D.C. | 202 | 202 + 7 digits |
| San Francisco | 415 | 415 + 7 digits |
| Houston | 713 | 713 + 7 digits |
| Miami | 305 | 305 + 7 digits |
| Boston | 617 | 617 + 7 digits |
Time difference (practical)
The UK is typically about five hours ahead of US Eastern. Central, Mountain, and Pacific time are further behind. DST schedules differ, so check the current offset before early or late calls.
How the international format is built
Under ITU-T E.164, the international number is the country code plus national significant number, with a maximum of 15 digits. The + symbol and spacing are access/display notation rather than E.164 digits.
Portable
+ 1 + 10-digit NANP
Digits-only from UK
00 + 1 + 10-digit NANP
Related routes and references
FAQ
What is the US country code from the UK?
1, written +1. From the UK dial 00 or +, then 1, then the full 10-digit NANP number. There is no trunk 0 to drop.
Do I dial 00 or +?
Use + on a mobile or saved contact when supported. Use 00 on a UK landline or digit-only path. After that, use 1 plus 10 digits.
Is there a zero to drop for US numbers?
No. Ordinary US numbers are 10 digits domestically. International form is +1 plus those same 10 digits.
Is +1 only for the United States?
No. +1 is shared by the North American Numbering Plan, including the US, Canada, and several Caribbean and Atlantic territories.
How do I dial a US mobile from the UK?
Use the same shape as a landline: 00 1 or +1, then the area code and seven digits. For example, (202) 555-01XX becomes 00 1 202 555 01XX or +1 202 555 01XX.
Standards and numbering-plan sources
- ITU-T E.164: The international public telecommunication numbering planInternational Telecommunication Union. Verified 2026-07-19.
- ITU-T E.123: Notation for national and international telephone numbersInternational Telecommunication Union. Verified 2026-07-19.
- The National Telephone Numbering PlanOfcom. Verified 2026-07-19.
- National numbering plan: United KingdomInternational Telecommunication Union. Verified 2026-07-19.
- National numbering plan: United StatesInternational Telecommunication Union. Verified 2026-07-19.
See our editorial and sourcing methodology.