International numbers confuse people for one simple reason: many countries use a trunk prefix for domestic calls that disappears when you dial from abroad. Once you understand it, every number format makes sense.
Three parts of an international call
- International access code: what you dial to leave your own country. It’s 00 in most of Europe and 011 in North America. On mobiles you simply press +.
- Country code: +44 UK, +49 Germany, +1 North America, +357 Cyprus.
- National number: the number without the domestic trunk prefix.
What the trunk prefix is
The trunk prefix tells a domestic network “this is a call to another area”. In the UK, Germany, France and many other countries it’s 0; in North America it’s 1. It’s only used inside the country.
| Country | Domestic | International | Trunk prefix |
|---|---|---|---|
| United Kingdom | 020 7946 0123 | +44 20 7946 0123 | 0 (dropped) |
| Germany | 030 1234567 | +49 30 1234567 | 0 (dropped) |
| France | 01 23 45 67 89 | +33 1 23 45 67 89 | 0 (dropped) |
| United States | 1 (212) 555-0123 | +1 212 555 0123 | 1 |
| Italy | 06 1234 5678 | +39 06 1234 5678 | none, the 0 is kept |
| Spain | 911 23 45 67 | +34 911 23 45 67 | none |
| Cyprus | 22 123456 | +357 22 123456 | none |
The exceptions
Italy and San Marino keep the leading 0 internationally, because it became part of the number itself. Spain, Portugal, Denmark, Norway, Greece and Cyprus have no trunk prefix at all, so the digits never change.
Every DIDNumbers country page lists its trunk prefix and international access code. For example, see the United Kingdom or Italy numbering tables.
The common mistake
Writing “+44 (0)20 7946 0123” is widespread in the UK, but the “(0)” isn’t valid in international format, and people abroad often dial it by mistake. Use +44 20 7946 0123 on websites and email signatures, or show both formats separately.
For systems and CRMs, store numbers in E.164 and let software handle the display.
Frequently asked questions
Do I dial the 0 when calling a UK number from a UK mobile?
Yes. Domestically you always dial the full number including the 0, or use +44 without the 0. Both work.
What’s the international access code from the US?
011, or simply + on a mobile phone.
See numbering facts for every country