How SMS Segmentation Works – What Happens When Your Message Is Too Long?
When you send a text message, you probably don't think about the technical details behind the scenes. But did you know there’s a character limit for SMS, and that longer messages are automatically split into multiple parts? In this guide, we explain how this works, what affects the limits, and why you might sometimes be able to send fewer characters than expected.
Basic Character Limits
A Standard SMS Can Contain:
- Up to 160 characters if using 7-bit encoding (commonly used for standard Latin letters, numbers, and basic symbols).
- Up to 70 characters if using Unicode encoding (required for things like emojis or languages that use special characters, such as Arabic or Chinese).
But what happens when your message exceeds these limits?
Multipart SMS (Concatenated SMS)
When an SMS exceeds the character limit, it is split into multiple parts. These parts are sent separately but are automatically reassembled on the recipient’s phone, so it appears as one continuous message.
For this to work, each part must include what's called a data header.This tells the recipient’s phone that the message is split—and how the parts should be reassembled. However, this extra information takes up a bit of space, which affects how many characters each part can actually contain.
How Many Characters Fit in Each Part?
When an SMS is split, the number of characters that fit in each part decreases
- 7-bit encoding:
➤ Instead of 160 characters per SMS part, you get 153 characters per part. 153 tecken per del. - Unicode encoding:
➤ Instead of 70 characters per SMS part, you get 67 characters per part. 67 tecken per del.
This is because 7 characters (or 3 in the case of Unicode) are reserved for the data header.
Why Is It Important to Know This?
If you send many or long SMS messages—such as in marketing campaigns or customer communications—it’s helpful to understand how splitting affects:
- Cost: More SMS parts mean higher costs per message sent.
- Experience: Although recipients see the message as a whole, some older devices might display the parts separately.
- Planning: You can optimize your message to keep it within one or two parts.
Want to keep track of how long your message is and how many parts it will be split into? Our web services include an automatic counter that shows exactly how many characters and SMS parts your message will consist of.
Summary:
| Encoding | Max Characters (Single SMS) | Max Characters (Concatenated SMS) |
|---|---|---|
| 7-bitars | 160 | 153 per part |
| Unicode | 70 | 67 per part |
By understanding how splitting works, you can plan your SMS campaigns more smartly—both from a cost and content perspective.
Character Limits per SMS Part Depending on Encoding
7-bit encoding
| Number of SMS parts | Characters per part | Total number of characters |
|---|---|---|
| 1 | 160 | 160 |
| 2 | 153 | 306 |
| 3 | 153 | 459 |
| 4 | 153 | 612 |
| 5 | 153 | 765 |
Unicode encoding
| Number of SMS parts | Characters per part | Total number of characters |
|---|---|---|
| 1 | 70 | 70 |
| 2 | 67 | 134 |
| 3 | 67 | 201 |
| 4 | 67 | 268 |
| 5 | 67 | 335 |