What Is E.164 Phone Number Format?

E.164 Format Explained Simply

An E.164 number has a maximum of 15 digits and always follows this basic structure:

An E.164 number contains no spaces, no dashes, no parentheses, and no dots. It starts with a plus sign (+), followed by the country code and the subscriber number in one machine-readable string.

Examples:

• +14155552671 — US number, country code 1
• +447700900077 — UK number, country code 44
• +4915123456789 — German number, country code 49
• +81901234567 — Japanese number, country code 81

Structure and Length Rules

The main rules are simple:

• Starts with a plus sign: Every E.164 number begins with +.
• Includes the country code: The number must include the international country dialing code.
• Maximum 15 digits: The digits after the plus sign cannot exceed 15 total digits.
• No local formatting characters: Spaces, dashes, dots, and parentheses are removed.

This is why a number like (415) 555-2671 often needs cleanup before import, while +14155552671 is already much closer to what systems expect.

Why CRMs, Dialers, and APIs Prefer E.164

Many CRMs, dialers, and communication APIs prefer E.164 because it gives them one consistent format for storing, routing, and comparing phone numbers. Here is why:

• Globally unique. A number like "555-1234" could belong to any country. "+15551234567" is unambiguous.
• Machine-readable. Systems can programmatically extract the country code, area code, and subscriber number without guessing.
• Routing. International calls and SMS messages require the country code to route correctly. Without it, delivery fails.
• Deduplication. "(415) 555-2671", "415-555-2671", and "4155552671" are all the same number. E.164 normalizes them to one canonical form.

E.164 Format Examples

Want to see the same idea in a realistic test file? Use the sample phone import CSV and compare the cleaned and needs-review outputs.

How Messy CSV Phone Data Gets Converted to E.164

Real CSV exports rarely start in perfect E.164 format. Phone cells often include spaces, punctuation, local formats, country-free numbers, or extra notes copied from spreadsheets and contact systems.

A CSV phone cleaner prepares that data for import by normalizing safe rows into E.164, preserving the rest of each row, and separating unclear rows into a needs-review file instead of guessing.

If you want the full step-by-step workflow, read how to clean phone numbers in a CSV before import or test the sample CSV.

Why Country Context Matters

Many CSV exports contain local-format numbers. For example, "07700 900077" may be valid in one country, but without country context a parser cannot safely convert it to E.164. It may be misread, normalized incorrectly, or sent to review.

This is why the normalizer lets you:

• Select a country column for per-row context (handles mixed-country data).
• Set a default country as a fallback for rows without an explicit country.

Numbers without any country context — and without a "+" prefix — should go to the Needs Review file instead of being guessed. For the full workflow, see how to clean phone numbers in a CSV before import.