What is GSM-7 character encoding in SMS?

GSM-7 character encoding is the standard format used for most SMS messages worldwide. It defines which characters can be included in a text message and how many characters fit into a single SMS.

Understanding GSM-7 character encoding helps businesses control message length, cost and delivery, especially when sending large volumes of SMS.

What GSM-7 character encoding means in SMS?

GSM-7 character encoding is the default encoding used in SMS messaging. It supports a specific set of characters designed for efficient text transmission.

A message using GSM-7 character encoding can contain up to 160 characters in a single SMS. This makes it the most cost efficient option when sending plain text messages.

GSM-7 character encoding is automatically applied as long as the message contains only supported characters.

Characters included in GSM-7 character encoding

The GSM-7 character set includes basic Latin letters, numbers and common symbols.

Examples of GSM-7 characters include:

• Uppercase and lowercase English letters
• Numbers from 0 to 9
• Basic punctuation such as commas and periods
• Common symbols like question marks and exclamation points

Some extended characters are also supported but they count as two characters instead of one.

GSM-7 character encoding vs Unicode in SMS

SMS messages use either GSM-7 character encoding or Unicode encoding. The encoding used affects how many characters fit into one message.

GSM-7 character encoding allows up to 160 characters in a single SMS. Unicode encoding supports a wider range of characters but limits a single SMS to 70 characters.

If a message contains even one character that is not supported by GSM-7 character encoding, the entire message is sent as Unicode.

This switch often happens without the sender noticing.

How GSM-7 character encoding affects SMS length

When GSM-7 character encoding is used, SMS messages follow these limits:

• Single SMS supports up to 160 characters
• Multipart SMS supports 153 characters per message part

Extended GSM characters such as certain symbols reduce the available character count because they require extra encoding space.

This means that a message can still be split even when GSM-7 character encoding is used.

Examples of GSM-7 character usage in SMS

The table below shows common examples of GSM-7 character usage and how it affects SMS messages.

When GSM-7 character encoding is not used

GSM-7 character encoding is not used when a message contains unsupported characters.

Common triggers that disable GSM-7 character encoding include:

• Emojis
• Accented characters like å é ñ
• Smart punctuation from copied text
• Currency symbols such as the euro sign
• Non Latin alphabets

When this happens, the message switches to Unicode and character limits are reduced.

Why GSM-7 character encoding is important for businesses

GSM-7 character encoding directly impacts SMS cost and efficiency. Messages that stay within GSM-7 limits are shorter, cheaper and less likely to be split into multiple parts.

For high volume SMS programs, using GSM-7 character encoding where possible helps control delivery costs and improves message predictability.

At the same time, avoiding necessary characters just to stay within GSM-7 can harm readability and local relevance.

How to manage GSM-7 character encoding effectively

Managing GSM-7 character encoding requires awareness of message content and character usage.

Best practices include:

• Reviewing message text before sending
• Avoiding unnecessary symbols and smart punctuation
• Testing messages across markets and languages
• Using SMS tools that show encoding and character count, such as the LINK Mobility SMS length calculator

With proper visibility, GSM-7 character encoding becomes easy to manage and plan around.

GSM-7 character encoding in global SMS communication

GSM-7 character encoding remains the foundation of SMS messaging. It supports fast, reliable and cost effective communication across markets.

For businesses operating internationally, understanding when GSM-7 character encoding applies and when Unicode is required helps balance cost, clarity and customer experience.

LINK Mobility SMS solutions support both GSM-7 character encoding and Unicode, giving businesses control over message content, length and delivery across global markets.