Phone numbers can be written in various ways—sometimes with spaces, dashes, parentheses, or without any separators. The choice of whether to include spaces or dashes depends largely on context, readability, international standards, and technical requirements. This discussion explores these factors to help you understand when and why to use spaces or dashes in phone numbers.
Readability and User Experience
One of the main reasons to include spaces or dashes in phone numbers is improving readability. Long strings of digits can be hard to read, remember, or accurately transcribe. Adding separators helps break the number into manageable chunks.
For example, consider this US phone number:
Without separators: 4155552671
With dashes: 415-555-2671
With spaces: 415 555 2671
The dashed or spaced versions are easier to read and less recent mobile phone number data prone to errors when typed or shared.
In many countries, common conventions have developed for grouping numbers:
United States: Often formatted as (415) 555-2671 or 415-555-2671.
United Kingdom: Typically written as 020 7946 0958 or 0207 946 0958.
France: Grouped as 01 23 45 67 89.
These formats reflect local dialing habits and conventions, helping users recognize and process the number quickly.
International Standards: E.164 Format
From a technical and international perspective, the E.164 phone number format—the global standard for phone numbers—does not include any spaces, dashes, or special characters. It requires a continuous string of digits, optionally starting with a “+” and country code, with a maximum length of 15 digits.
For example:
+14155552671
This format is essential for telecommunications systems, databases, and APIs to parse, route, and validate phone numbers unambiguously.
When to Use or Avoid Spaces/Dashes
User Interfaces & Printed Materials: Spaces or dashes are highly recommended to enhance human readability. For example, websites, business cards, advertisements, and user forms often display phone numbers with separators.
Storage & Processing: When storing or transmitting phone numbers in databases, APIs, or telecom systems, phone numbers should be saved in the clean E.164 format without separators. This prevents parsing errors and ensures compatibility across systems.
Input Fields: User input fields sometimes accept spaces or dashes to aid typing, but these characters are usually stripped out by validation logic before further processing.
Guidelines for Formatting Phone Numbers
Display for Humans: Use spaces or dashes consistent with local conventions to improve clarity. For example:
UK: +44 20 7946 0958
USA: +1 415-555-2671
Store & Transmit for Machines: Use the E.164 format without any spaces or dashes. For example:
+14155552671
Input Handling: Accept input flexibly, allowing users to enter spaces or dashes, but normalize internally.
Summary
Spaces and dashes improve readability and reduce input errors when phone numbers are displayed to users.
E.164 format excludes spaces and dashes for consistent international communication and data processing.
It is best practice to display numbers with separators but store and transmit them in the clean E.164 format.