SMS Character Counter

How parts work differently for GSM-7 and Unicode

When an SMS exceeds 160 characters, it’s split into multiple parts through a process called concatenation. The number of characters per part depends on the encoding used—either GSM-7 or Unicode.

The main difference is how many characters each part can hold. GSM-7 allows more characters per part than Unicode, which uses additional space for encoding non-standard characters like emojis or non-Latin scripts.

Although messages are technically split, the recipient will see a single, seamless message. These parts may be billed individually, but they’re visually combined into one message.

Example breakdown

GSM-7 (Standard Characters
Supports up to 153 characters per part (160 for single-part messages). Extra space is used for metadata that links message parts.

 • 100 characters → 1 part
 • 170 characters → 2 parts (153 + 17)
 • 320 characters → 3 parts (153 + 153 + 14) 

Unicode (Non-GSM Characters)
Supports only 67 characters per part due to higher metadata overhead. Needed for emojis and non-Latin scripts.

 • 100 characters → 2 parts (67 + 33)
 • 170 characters → 3 parts (67 + 67 + 36)
 • 320 characters → 5 parts (67 + 67 + 67 + 67 + 52)

What is SMS concatenation?

SMS concatenation links multiple message parts into one seamless message for the recipient. Each part includes headers that tell the device it’s part of a longer message.

How many parts can be concatenated?
Typically, up to 3 parts (or 460 characters in GSM-7) can be concatenated into one message, depending on the carrier and device. After 3 parts, the message might be split into a new visual SMS, but the total number of parts will still be billed separately. For Unicode messages, since fewer characters fit per part, a message may break into 4 or more parts for longer messages.

Why this matters for billing
Each part is counted separately for billing purposes, and customers are charged for every part required to send the message. Since GSM-7 can fit more characters per part, messages encoded in GSM-7 generally require fewer parts, leading to lower costs compared to Unicode.

For example:
• A 170-character message sent using GSM-7 will require 2 parts (153 + 17 characters).
• The same 170-character message sent using Unicode will require 3 parts (67 + 33 + 70 characters).

Although the message looks like one message, costs are based on the total number of parts sent.