> ## Documentation Index
> Fetch the complete documentation index at: https://kero.chat/help/llms.txt
> Use this file to discover all available pages before exploring further.

# SMS message length & character limits

> Understand SMS character limits, message parts and how GSM and Unicode encoding affect your SMS messages.

SMS messages have character limits. If your message exceeds the limit for a single SMS, Kero automatically divides it into multiple **message parts**.

The number of characters available in each part depends on whether your message uses **GSM** or **Unicode** encoding.

> [!NOTE]
>
> Each SMS part is generally billed separately. Message length and encoding can therefore affect the cost of sending your message.

## Understanding SMS message parts

An SMS can contain one or more message parts.

A short message normally uses **one part**.

When the message exceeds the character limit for a single SMS, it becomes a **multipart SMS** and is divided into two or more parts.

The recipient's phone normally joins these parts together and displays them as one continuous message.

For example:

| Message | Parts |
| - | - |
| Short SMS within the character limit | 1 |
| Longer SMS exceeding the single-part limit | 2 or more |

Kero shows the number of **Characters** and **Parts** while you compose an SMS.

> [!NOTE]
>
> The recipient normally sees one message even when it is sent as multiple SMS parts.

## GSM character limits

Most standard SMS messages use the **GSM character set**.

A single GSM SMS can contain up to **160 characters**.

When a GSM message exceeds 160 characters, it becomes a multipart SMS.

Each part can then contain up to **153 characters**.

Some space in each part is reserved for information that allows the recipient's device to join the message parts together.

| GSM message | Character limit |
| - | -: |
| 1 part | 160 |
| 2 parts | 306 |
| 3 parts | 459 |
| 4 parts | 612 |

For example, a GSM message containing **170 characters** requires **2 SMS parts**.

> [!NOTE]
>
> These limits assume the message uses standard GSM characters. Extended GSM characters require additional encoding space and can reduce the amount of text that fits into each part.

## Extended GSM characters

Some characters are supported by GSM but require additional space when encoded.

Examples include:

* `^`
* `{` and `}`
* `\`
* `[` and `]`
* `~`
* `|`
* `€`

These characters use **two character positions** when calculating the encoded SMS length.

For example, the text `Hello {Alex}` contains 12 visible characters but uses 14 GSM character positions because `{` and `}` each require two positions.

> [!NOTE]
>
> The **Characters** indicator in Kero helps you understand the encoded message length. Extended GSM characters can cause the SMS part count to increase sooner than expected.

## Unicode character limits

If your message contains characters that aren't supported by the GSM character set, it may need to use **Unicode** encoding.

Unicode supports a much wider range of characters and languages.

A single Unicode SMS can contain up to **70 characters**.

When a Unicode message exceeds 70 characters, each multipart SMS part can contain up to **67 characters**.

| Unicode message | Character limit |
| - | -: |
| 1 part | 70 |
| 2 parts | 134 |
| 3 parts | 201 |
| 4 parts | 268 |

Because Unicode has a lower character limit, a Unicode message may use more SMS parts than a similar GSM message.

> [!NOTE]
>
> These are standard Unicode SMS limits, measured in encoding units. Some characters, including many emojis, use more than one unit and may reduce the number of visible characters that fit into a message.

## What can cause an SMS to use Unicode?

Unicode may be required when your message contains characters that aren't part of the GSM character set.

This can include:

* Characters from some non-Latin writing systems
* Certain accented or special characters
* Typographic punctuation
* Some symbols
* Emojis

Sometimes a character that looks very similar to a standard GSM character can cause the entire message to use Unicode.

For example, copying text from a document or website may introduce typographic characters such as curly quotation marks.

> [!WARNING]
>
> **A single unsupported character can affect the encoding of your entire SMS.**
>
> When Unicode conversion is enabled, a character outside the GSM character set can cause the message to use Unicode, reducing the number of characters available per SMS part.
>
> When Unicode conversion is disabled, Kero removes unsupported characters instead.

## GSM and Unicode compared

| Encoding | Single SMS | Multipart SMS |
| - | -: | -: |
| GSM | 160 characters | 153 characters per part |
| Unicode | 70 characters | 67 characters per part |

The difference becomes more significant as messages get longer.

For example, a message containing **200 characters** would normally require:

* **2 parts** using GSM
* **3 parts** using Unicode

These examples assume each character occupies one encoding position or unit.

## Check your message in Kero

When you write an SMS directly in Kero, the **SMS Text** field shows:

* **Characters:** The length of your message
* **Parts:** The number of SMS parts required
* **Encoding:** Whether the message uses GSM or Unicode

These values update as you type.

Use them to check your message before sending.

> [!NOTE]
>
> Pay particular attention to the **Parts** indicator. This shows how many SMS parts your message requires and helps you understand its potential cost.

## Automatically convert to Unicode

When you create an SMS Agent, Kero includes an **Automatically convert to Unicode** setting.

This setting determines how Kero handles characters that are not supported by the standard GSM character set.

### When enabled

Kero uses Unicode encoding when the message contains characters outside the GSM character set.

This preserves characters such as emojis, typographic punctuation and characters from other writing systems.

However, Unicode messages have lower character limits per SMS part, which may increase the cost of sending your message.

### When disabled

Kero removes characters that are not supported by the standard GSM character set.

This can help avoid switching the message to Unicode, but it may also change the content or meaning of your message.

For example, an unsupported emoji or typographic character may be removed rather than included in the delivered SMS.

> [!WARNING]
>
> **Important: Unsupported characters are removed when Automatically convert to Unicode is disabled.**
>
> Review your message content and preview carefully before sending. Removing characters may affect punctuation, words or the intended meaning of your message.

You can review this setting when you [set up your SMS Agent](https://kero.chat/help/product/channels/sms/setup-your-sms-agent.md).

## Keep SMS messages efficient

Before sending a message, check:

* The **Characters** count
* The **Parts** count
* Whether Kero shows **GSM** or **Unicode**
* Whether unusual characters are increasing the message length
* Whether any unsupported characters have been removed
* Whether the message can be shortened without changing its meaning

For campaigns with large audiences, even one additional SMS part per recipient can significantly increase the total number of SMS messages sent.

> [!NOTE]
>
> If you're using an SMS template, remember that parameter values can change the final message length.
>
> Longer values or Unicode characters introduced through personalisation may cause the completed message to use additional SMS parts.


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