Quick answer: The international phone number format is the E.164 standard from the ITU. Every number breaks into four parts: a leading +, a 1- to 3-digit country code, a national destination code (area code or mobile prefix), and the subscriber number — capped at 15 digits total. To convert any local number: add
+and the country code, drop the trunk 0 if there is one, keep the rest intact. A US number(202) 555-0173becomes+1 202 555 0173. A UK number020 7946 0958becomes+44 20 7946 0958. Store every number in E.164 form everywhere and your CRMs, SMS, and APIs will all stop breaking.
International phone number format: a plain-English guide
A phone number that works perfectly at home can fail completely when dialed from abroad. Drop the country code, keep a leading zero, or guess the spacing — and the call simply does not connect.
This guide explains the one standard that fixes all of that: E.164. You will learn how the format is built, the rules behind country codes and the plus sign, how to convert a local number, and the mistakes that quietly break international calls.
What is the E.164 standard?
E.164 is the global rulebook for phone numbers. It is an official ITU recommendation — formally "the international public telecommunication numbering plan."
Why a global standard exists
Every country built its own dialing habits over decades. Without a shared format, a number from Brazil would be unreadable to a network in Japan.
E.164 solves that by defining one structure every network on Earth can parse the same way. It is what makes a phone call cross borders without a translator.
The 15-digit rule
An E.164 number contains digits only — no letters, no spaces in its strict form — and never exceeds 15 digits total.
That 15-digit ceiling has applied worldwide since 1997. Before that, the limit was 12.
The four parts of an international number
Every correctly formatted number breaks into the same pieces. Once you can see them, the format stops feeling random.
Part 1: The plus sign
The leading + is not decoration. It tells any phone or system: "an exit code goes here." It stands in for the digits you would otherwise dial to leave your country (011 in the US, 00 across much of Europe).
A number saved as +1 202 555 0173 dials correctly from London, Lagos, or Lima. The same number without the + may fail abroad.
Part 2: The country code
This is a 1 to 3 digit code unique to each country. The United States and Canada use +1, the UK uses +44, India uses +91.
Part 3: The national destination code
Often called the area code or mobile prefix, this identifies a region or network inside the country. It is the next block of digits after the country code.
Part 4: The subscriber number
This is the individual line itself. The country code, destination code, and subscriber number together stay within the 15-digit limit.
Building a contact form, CRM, or SMS list? Storing every number in E.164 form from the start saves hours of cleanup later. MCM provisions numbers across 190+ countries already in the correct format.
Hazır olduğunuzda hazır
İş hattınızı koruyun.
MCM'nin yerel numaraları, doğrulanmış arayan kimliği ve akıllı çağrı filtrelemeyle birlikte gelir; müşteriler her zaman gerçekte siz olduğunuzu bilir ve spam ekibinize asla ulaşmaz.
How to convert a local number to international format
The conversion follows the same three steps for almost every country.
Step 1: Add the country code
Find the destination's country code and place it after a + symbol. For Germany that is +49, for Japan +81.
Step 2: Drop the trunk zero
Many countries use a leading 0 for domestic calls — common in the UK, Germany, and Australia. That trunk zero is removed in international format.
So a UK number written 020 7946 0958 becomes +44 20 7946 0958. The 0 disappears.
Step 3: Keep the rest intact
After the country code is added and the trunk zero removed, the remaining digits stay exactly as they are. Spacing is for readability only — networks read the digits.
Want this as a quick reference? Save the country-code table below, or let MCM hand you numbers that are already E.164-ready so there is nothing to convert.
Country code quick reference
Here is how the format looks across major markets. Note the trunk-zero rule in action.
| Ülke | Country code | Example in E.164 format |
|---|---|---|
| United States / Canada | +1 | +1 202 555 0173 |
| Birleşik Krallık | +44 | +44 20 7946 0958 |
| Almanya | +49 | +49 30 123456 |
| Fransa | +33 | +33 1 23 45 67 89 |
| Hindistan | +91 | +91 98765 43210 |
| Avustralya | +61 | +61 2 9876 5432 |
| Japan | +81 | +81 3 1234 5678 |
| Brezilya | +55 | +55 11 91234 5678 |
| Nigeria | +234 | +234 1 234 5678 |
| South Africa | +27 | +27 11 234 5678 |
Common formatting mistakes to avoid
These small slips cause most failed international calls and rejected form submissions.
Forgetting the country code
A number without a country code is only valid inside one country. For anything crossing a border, the code is mandatory.
Keeping the trunk zero
Leaving the domestic leading 0 in place is the single most frequent error. In international format, that 0 is replaced by the country code, not kept alongside it.
Mixing letters into the number
Vanity numbers like 1-800-FLOWERS look friendly but are not E.164 valid. Systems need the pure digit version.
Inconsistent storage
Saving some numbers with a +, some without, and some with stray spaces breaks validation. Pick E.164 and apply it everywhere.
Why this matters for modern business
Getting the format right is not just about one phone call connecting.
It powers SMS, CRMs, and APIs
Messaging platforms, customer databases, and calling APIs nearly all expect E.164 input. A messy number list means failed texts and broken automations.
It supports a global presence
A business serving customers in several countries needs numbers that route reliably from anywhere. Consistent formatting is the quiet foundation of that.
MCM provisions local, toll-free, and DID numbers across 190+ countries, each delivered in standard E.164 format and ready to plug into your systems.
Final word
The international phone number format is less complicated than it first looks. Three parts, a plus sign, and one habit — drop the trunk zero — cover almost every case.
Start storing every number in E.164 form today. Your CRM, your SMS campaigns, and your support team will all run smoother for it.
When you need numbers that arrive correctly formatted from the start, MCM has them ready across 190+ countries.
Hazır olduğunuzda hazır
Satış yaptığınız her yerde yerel görünmeye hazır mısınız?
MCM, çağrı yönlendirme, analiz ve CRM'ye hazır entegrasyonlarla işletme numaralarını dakikalar içinde etkinleştirir. Ücretsiz denemenizi başlatın; envantere göz atmak için kart yok.
Frequently asked questions
What is the international phone number format?
It is a standardized way of writing phone numbers, defined by the E.164 standard, so they can be dialed correctly from any country. It uses a + sign, a country code, and the national number.
What is the E.164 standard?
E.164 is an ITU recommendation that defines the global numbering plan for phone networks. It limits numbers to 15 digits and splits them into a country code and a national number.
Why do international numbers start with a plus sign?
The + replaces the country-specific exit code (like 011 or 00). It lets one stored number dial correctly from anywhere without knowing the local exit prefix.
Do I remove the leading zero in international format?
Usually yes. Many countries use a trunk 0 for domestic calls, and that 0 is dropped when you add the country code for international format.
What is the maximum length of an international phone number?
Under E.164, a phone number can be no longer than 15 digits in total, including the country code.
How do I convert a US number to international format?
Add +1 in front of the 10-digit number. For example, (202) 555-0173 becomes +1 202 555 0173.
Why should businesses store numbers in E.164 format?
Most CRMs, SMS platforms, and calling APIs require E.164 input. Consistent formatting prevents failed messages, broken automations, and dialing errors.
Get E.164-ready numbers from MCM
Building a global presence shouldn't mean wrangling formats across 50 systems.
My Country Mobile provisions local, toll-free, and DID numbers across 190+ countries, every line delivered in standard E.164 form and ready to drop straight into your CRM, contact center, or SMS platform.
Call forwarding, voicemail-to-email, SMS, and AI transcription are all included, and over 17,500 businesses already trust MCM with their international phone presence.
