International Phone Number Formatting Standards

Phone numbers look different around the world. A number that makes perfect sense in one country can confuse someone in another if it isn’t formatted properly. Whether you’re building a contact database, printing business cards for international clients, or setting up a phone system, understanding formatting standards prevents miscommunication and failed calls.

This guide covers the internationally recognized formats, explains country-specific conventions, and gives practical advice for different use cases.

The E.164 International Standard

The International Telecommunication Union (ITU) established E.164 as the global standard for phone number formatting. It’s the format used by virtually all telecommunications systems, APIs, and databases worldwide.

An E.164 number consists of:

• A plus sign (+) indicating international format
• The country code (1 to 3 digits)
• The subscriber number (remaining digits, up to a total of 15 digits)

Examples:

• United States: +14155552671
• United Kingdom: +442071234567
• Japan: +81312345678
• Australia: +61412345678

E.164 numbers contain no spaces, hyphens, parentheses, or other formatting characters. This makes them ideal for storage and transmission because there is zero ambiguity about how to dial the number from anywhere in the world.

Country Code Basics

Every country (and some territories) has a unique country calling code assigned by the ITU. Some of the most commonly used codes include:

Country	Code	Example
United States/Canada	+1	+1 212 555 1234
United Kingdom	+44	+44 20 7123 4567
Germany	+49	+49 30 12345678
France	+33	+33 1 23 45 67 89
Australia	+61	+61 2 1234 5678
Japan	+81	+81 3 1234 5678
India	+91	+91 98765 43210
Brazil	+55	+55 11 91234 5678

An important detail: when you add the country code, you typically drop the leading zero from the national number. For example, a UK number dialed domestically as 020 7123 4567 becomes +44 20 7123 4567 in international format. The leading zero is a trunk prefix used only for domestic calls.

National Formatting Conventions

Each country has its own conventions for how numbers appear in printed materials, on websites, and in everyday use.

United States and Canada

The North American Numbering Plan uses a consistent 10-digit format:

• (212) 555-1234 (most common printed format)
• 212-555-1234 (common alternative)
• +1 212-555-1234 (international format with visual separators)

The three-digit area code identifies the region, the three-digit exchange narrows it further, and the four-digit subscriber number identifies the individual line.

United Kingdom

UK numbers vary in length depending on the type:

• London landlines: 020 xxxx xxxx (11 digits total)
• Mobile numbers: 07xxx xxxxxx (11 digits)
• Other geographic: 01xxx xxxxxx or 01xxxx xxxxx

The leading zero is the trunk prefix. When writing in international format, it is replaced by +44.

Germany

German numbers have variable-length area codes (2 to 5 digits) and subscriber numbers:

• Berlin: 030 12345678
• Munich: 089 12345678
• Smaller cities: 05251 123456

International format: +49 followed by the number without the leading zero.

Japan

Japanese numbers follow an area code system where major cities have shorter area codes:

• Tokyo: 03-1234-5678
• Osaka: 06-1234-5678
• Mobile: 090-1234-5678

Formatting for Different Contexts

The right format depends on where and how the number will be used.

Database Storage

Always store numbers in E.164 format. This eliminates ambiguity and makes numbers sortable, searchable, and dialable by automated systems. Strip all spaces, hyphens, and parentheses before saving.

• Store: +14155552671
• Do not store: (415) 555-2671 or 415.555.2671

If your system serves a single country, you might store the national number without the country code, but this creates problems if you ever expand internationally. Starting with E.164 saves future headaches.

Business Cards and Letterheads

For printed materials, use the international format with visual grouping for readability:

• +1 (415) 555-2671 (US number on an international business card)
• +44 20 7123 4567 (UK number)
• +81 3-1234-5678 (Japanese number)

Include the country code even if your audience is primarily domestic. Business cards travel, and recipients in other countries need the full number to make the call.

Websites and Email Signatures

Use the clickable tel: link format for websites:

+1 (415) 555-2671

The href uses the E.164 format (no spaces or punctuation) so mobile devices can dial it directly, while the visible text uses a human-friendly format.

SMS and Messaging Platforms

Most messaging platforms (WhatsApp, Signal, Telegram) require the full international number with country code, typically in E.164 format without the plus sign or with it depending on the platform. When sharing your number for messaging, always include the country code.

Common Formatting Mistakes

Forgetting to Drop the Trunk Prefix

The most common error when converting to international format is keeping the leading zero:

• Wrong: +44 020 7123 4567
• Right: +44 20 7123 4567

Using Inconsistent Separators

Pick one separator style and stick with it. Mixing formats looks unprofessional:

• Inconsistent: +1 (415) 555.2671
• Consistent: +1 (415) 555-2671

Omitting the Country Code for International Audiences

If your website or document reaches people outside your country, a number without a country code is useless to international visitors. Always include it.

Confusing Exit Codes with Country Codes

An exit code (like 011 in the US or 00 in Europe) is what you dial to reach the international network from a landline. It’s not part of the phone number itself. The plus sign in E.164 format replaces whatever exit code the caller’s country uses.

Extension Numbers

For business numbers with extensions, place the extension after the main number, separated by a comma or the abbreviation “ext.”:

• Print: +1 (415) 555-2671 ext. 302
• Database: +14155552671,302 (comma causes a pause when auto-dialed)

Vanity Numbers

Vanity numbers use letters on the phone keypad to spell words (1-800-FLOWERS). While memorable, they should always be accompanied by the numeric equivalent for international callers, since keypad letter assignments differ between countries.

Use the Tool

Formatting numbers by hand is tedious, especially when processing a list of contacts from different countries. Our Phone Number Formatter takes numbers in any common format and outputs them in the standard you need, whether that is E.164 for your database or a human-readable international format for printed materials.

Frequently Asked Questions

What is the maximum length of a phone number?

Under the E.164 standard, the maximum total length is 15 digits, including the country code. The shortest valid numbers are around 7 digits total (some small countries). Most numbers fall between 10 and 13 digits including the country code.

Why do some countries have variable-length phone numbers?

This dates back to when phone systems were designed. Large cities with more subscribers needed more digits, so they received shorter area codes paired with longer subscriber numbers. Smaller areas got longer area codes with shorter local numbers. Countries like the US and Canada standardized to a fixed 10-digit format, but many European and Asian countries still use variable lengths.

Should I store the plus sign in my database?

Yes. Including the plus sign (or storing it as the text ”+”) is the standard E.164 practice and makes it unambiguous that the number is in international format. If your database schema doesn’t support the plus sign, store it as a separate boolean field or column indicating the number is in E.164 format.

How do I format a number if I don’t know the country of origin?

Without the country code, you can’t reliably format a number into international standard. If you have the caller’s IP address or billing address, you can infer the country. Otherwise, ask the user to select their country or provide the number with the country code included.

Do mobile and landline numbers follow the same formatting rules?

They follow the same E.164 structure, but their national formatting conventions often differ. In many countries, mobile numbers have distinct prefixes (07 in the UK, 04 in Australia) and may be a different length than landline numbers. When storing them in E.164 format, the distinction doesn’t matter since both types are treated the same way.