# SMS segments and message length

## **Message Encoding**

SMS messages can be encoded using different character sets, notably GSM-7, ISO-8859-1 and Unicode. The choice of encoding impacts the maximum length of a message and the number of segments required for transmission.

## **Types of Encoding**

### **GSM-7 (7bit)**

GSM-7 encoding, the standard for SMS messages, accommodates most characters within its 128 Latin characters, numbers, and select special characters repertoire. Each character occupies one slot within the message, allowing for a maximum message length of **160 characters**.

#### GSM-7 Encoding Characters

<table data-header-hidden data-full-width="false"><thead><tr><th width="87"></th><th width="87"></th><th width="87"></th><th width="87"></th><th width="87"></th><th width="87"></th><th width="87"></th><th width="87"></th></tr></thead><tbody><tr><td>@</td><td>Δ</td><td><em><strong>SP*</strong></em></td><td>0</td><td>¡</td><td>P</td><td>¿</td><td>p</td></tr><tr><td>£</td><td>_</td><td>!</td><td>1</td><td>A</td><td>Q</td><td>a</td><td>q</td></tr><tr><td>$</td><td>Φ</td><td>"</td><td>2</td><td>B</td><td>R</td><td>b</td><td>r</td></tr><tr><td>¥</td><td>Γ</td><td>#</td><td>3</td><td>C</td><td>S</td><td>c</td><td>s</td></tr><tr><td>è</td><td>Λ</td><td>¤</td><td>4</td><td>D</td><td>T</td><td>d</td><td>t</td></tr><tr><td>é</td><td>Ω</td><td>%</td><td>5</td><td>E</td><td>U</td><td>e</td><td>u</td></tr><tr><td>ù</td><td>Π</td><td>&#x26;</td><td>6</td><td>F</td><td>V</td><td>f</td><td>v</td></tr><tr><td>ì</td><td>Ψ</td><td>'</td><td>7</td><td>G</td><td>W</td><td>g</td><td>w</td></tr><tr><td>ò</td><td>Σ</td><td>(</td><td>8</td><td>H</td><td>X</td><td>h</td><td>x</td></tr><tr><td>Ç</td><td>Θ</td><td>)</td><td>9</td><td>I</td><td>Y</td><td>i</td><td>y</td></tr><tr><td><em><strong>LF*</strong></em></td><td>Ξ</td><td>*</td><td>:</td><td>J</td><td>Z</td><td>j</td><td>z</td></tr><tr><td>Ø</td><td><em><strong>ESC*</strong></em></td><td>+</td><td>;</td><td>K</td><td>Ä</td><td>k</td><td>ä</td></tr><tr><td>ø</td><td>Æ</td><td>,</td><td>&#x3C;</td><td>L</td><td>Ö</td><td>l</td><td>ö</td></tr><tr><td><em><strong>CR*</strong></em></td><td>æ</td><td>-</td><td>=</td><td>M</td><td>Ñ</td><td>m</td><td>ñ</td></tr><tr><td>Å</td><td>ß</td><td>.</td><td>></td><td>N</td><td>Ü</td><td>n</td><td>ü</td></tr><tr><td>å</td><td>É</td><td>/</td><td>?</td><td>O</td><td>§</td><td>o</td><td>à</td></tr></tbody></table>

* ***LF*** is a Line Feed control
* ***CR*** is a Carriage Return control, or filler
* ***ESC*** is an Escape to extension table
* ***SP*** is a Space character

The following characters are included in the GSM-7 character set, but they represent two characters when used in a text message:

```
\ ^ [ ] { } | ~ €
```

### ISO-8859-1 (Latin-1)

ISO-8859-1 is an 8-bit encoding that serves as an intermediate option when a message contains characters that are not present in GSM-7 but are included in the extended Latin set (the first 256 Unicode characters). Each character takes 8 bits, which limits the maximum length of a single message to **140 characters**. When a message is segmented, each part is **134 characters** long.

{% hint style="info" %}
The most common example is the non-breaking space. It looks like a regular space but has a different code. If it is copied from a text editor or a web page, the text will be in a different encoding. This can cause the character limit to drop from 160 to 140.
{% endhint %}

| ␀    | ␁    | ␂    | ␃    | ␄    | ␅    | ␆    | ␇    |
| ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- |
| ␈    | TAB  | VT   | ␎    | ␏    | ␐    | ␑    | ␒    |
| ␓    | ␔    | ␕    | ␖    | ␗    | ␘    | ␙    | ␚    |
| ␛    | ␜    | ␝    | ␞    | ␟    | \`   | ␡    | ⟨C1⟩ |
| ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ |
| ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ |
| ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ |
| ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | ⟨C1⟩ | NBSP |
| ¢    | ¦    | ¨    | ©    | ª    | «    | ¬    | SHY  |
| ®    | ¯    | °    | ±    | ²    | ³    | ´    | µ    |
| ¶    | ·    | ¸    | ¹    | º    | »    | ¼    | ½    |
| ¾    | À    | Á    | Â    | Ã    | È    | Ê    | Ë    |
| Ì    | Í    | Î    | Ï    | Ð    | Ò    | Ó    | Ô    |
| Õ    | ×    | Ù    | Ú    | Û    | Ý    | Þ    | á    |
| â    | ã    | ç    | ê    | ë    | í    | î    | ï    |
| ð    | ó    | ô    | õ    | ÷    | ú    | û    | ý    |
| þ    | ÿ    |      |      |      |      |      |      |

* **␀–␟** — C0 control characters (U+0000–U+001F), non-printable.
* **⟨C1⟩** — C1 control characters (U+0080–U+009F), non-printable.
* **TAB** — Horizontal Tab (U+0009).
* **VT** — Vertical Tab (U+000B).
* **␡** — Delete (DEL, U+007F).
* **NBSP** — No-Break Space (U+00A0).
* **SHY** — Soft Hyphen (U+00AD; discretionary hyphen, often invisible unless a line breaks).

### **Unicode**

Unicode encoding supports a broader spectrum of characters, including non-Latin languages, emojis, and special symbols. However, each Unicode character occupies two slots, effectively halving the maximum message length to **70 characters**.

## **SMS segments**

When an SMS message exceeds the character limit, it undergoes segmentation, dividing it into multiple segments for delivery. Each segment, although sent separately, is seamlessly reassembled on the recipient's device to form the original message.

{% hint style="info" %}
Each segment is charged separately.
{% endhint %}

## **Maximum number of** segments

SMS segmentation is not without limitations. Exceedingly long messages may not be delivered, as carrier networks have constraints on the maximum message length. For GSM-7 messages, the maximum length is 1377 characters, while for Unicode messages, it's 603 characters.

## **Best Practices**

To optimize your SMS campaigns:

* Keep messages concise and within recommended character limits to ensure successful delivery.
* Use GSM-7 encoding for messages containing only Latin characters and numbers, and Unicode for messages with non-Latin characters, emojis, or special symbols.
* Avoid excessive use of special characters or formatting to minimize the number of segments required for transmission.

Understanding the dynamics of SMS message length and segmentation empowers you to craft impactful messages that resonate with your audience. By adhering to best practices and leveraging the insights provided, you can enhance delivery rates, improve recipient experience, and boost engagement in your SMS campaigns. Should you have any inquiries or require further assistance, our [Support team](https://app.miatel.com/help) is readily available to assist you.


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