> For the complete documentation index, see [llms.txt](https://docs.emaillabs.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.emaillabs.io/en/sms/sms-campaings/campaigns/creating-a-new-sms-campaign/content/message-billing-rules.md).

# Message Billing Rules

* **GSM-7 Characters** - Standard characters used in SMS messages. One SMS can contain up to **160 characters** in this standard.
* If the message includes special characters, their use is automatically detected and displayed below the editor.
  * Using special characters reduces the length of one SMS from 160 to **70 characters**.
  * For messages containing special characters, confirm your consent to send content with such characters.

{% hint style="info" %}
**Note!** Using personalization in the message content may also increase the message length and the number of billing units. To ensure personalization works correctly, account for potential message length increases depending on the data entered in the personalized field.
{% endhint %}