Although SMS messages have character limits, recipients will generally receive your message as one continuous message on their device. Long messages are automatically joined together behind the scenes and are not delivered as separate SMS messages.

SMS Character Types

There are two character sets used in SMS messaging:

Standard (GSM) Characters

These are characters included in the GSM 03.38 character set, which covers:

• Standard English letters (A-Z, a-z)
• Numbers (0-9)
• Common punctuation and symbols

Messages containing only GSM characters can use the maximum SMS character allowance.

Unicode Characters

Unicode characters include anything outside the GSM character set, such as:

• Emojis 😊
• Smart quotes (“ ”)
• Curly apostrophes (’)
• Accented characters (é, ñ, ü)
• Non-Latin alphabets and special symbols

If your message contains even a single Unicode character, the entire message is encoded as Unicode, significantly reducing the number of characters available per SMS part.

Important: Emojis and special characters can dramatically increase the number of SMS parts used by a message.

GSM SMS Length

A standard GSM SMS can contain up to 160 characters.

Once a message exceeds 160 characters, it becomes a multi-part SMS. To allow mobile networks to reassemble the message correctly, each additional part reserves space for invisible message headers.

As a result:

• First SMS part: 160 characters
• Multi-part SMS: 153 characters per part

GSM Character Limits

Example

A 280-character GSM message would be sent as:

• Part 1: 153 characters
• Part 2: 127 characters

This would be billed as 2 SMS parts, but delivered to the recipient as a single message.

Unicode SMS Length

Unicode messages have a lower character limit because they require a different encoding format.

• Single Unicode SMS: 70 characters
• Multi-part Unicode SMS: 67 characters per part

Unicode Character Limits

Example

A 150-character message containing an emoji 😀 would be encoded as Unicode and use:

• Part 1: 67 characters
• Part 2: 67 characters
• Part 3: 16 characters

This would be billed as 3 SMS parts even though the message is only 150 characters long.

How SMS Parts Affect Billing

SMS charges are typically based on the number of message parts used, not the number of messages sent.

For example:

• 150 GSM characters = 1 SMS part
• 300 GSM characters = 2 SMS parts
• 700 GSM characters = 5 SMS parts
• 150 Unicode characters = 3 SMS parts

For this reason, avoiding unnecessary Unicode characters can help reduce SMS costs.

Common Characters That Trigger Unicode Encoding

The most common causes of Unicode messages are:

• Emojis 😊
• Curly apostrophes (’)
• Curly quotation marks (“ ”)
• Bullet symbols (•)
• Long dashes (—)
• Accented characters (é, è, ü, ñ)

Whenever possible, use standard keyboard characters instead:

• ' instead of ’
• " instead of “ or ”
• - instead of —

Maximum SMS Length

Most modern mobile networks support messages up to 8 message parts.

This means the practical maximum length is:

GSM Messages

• Up to 1,224 characters (8 parts)

Unicode Messages

• Up to 536 characters (8 parts)

Messages exceeding these limits may be truncated or rejected by the recipient’s carrier.

Best Practices

• Keep messages concise where possible
• Avoid emojis and special characters unless required
• Use standard apostrophes and quotation marks
• Review the SMS part counter before sending large campaigns
• Remember that billing is based on SMS parts, not individual messages

By understanding GSM and Unicode character limits, you can optimise message length, reduce SMS costs, and ensure reliable delivery to your recipients