> For the complete documentation index, see [llms.txt](https://support.caspen.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://support.caspen.com/using-caspen/settings/billing/sms-character-limits-and-credit-usage-guide.md).

# SMS character limits and credit usage guide

## Overview

Caspen uses standard SMS rules, which determine how long a message can be before it is split into segments. This is useful to know when writing appointment or class notifications, since longer messages can use more SMS credits.

***

## How SMS segments work

#### **Standard GSM characters**: 

* 1 segment = **160** characters. 
* Long messages use **153** characters per segment.

#### **With emojis or special characters**: 

* 1 segment = **70** characters. 
* Long messages use **67** characters per segment.

***

#### **What counts as standard GSM**

* Letters, numbers, spaces, and common punctuation (A–Z, a–z, 0–9, . , ! ? ' " : ; ( ) / @ #).

***

#### **Special characters**

Special characters include:

* Curly quotes **“ ”** and **‘ ’**
* Long dashes
* Many accented letters (for example, **é** or **ü**)
* Symbols such as **{ } \[ ] ^ \ |**
* Emojis

Using emojis or special characters reduces how many characters fit in one SMS, which may increase the number of segments (and credits) used.

***

## **Cost**

You use **1 SMS credit per outbound segment**.

***

## **Tips to reduce SMS costs**

* Keep SMS short and clear. 
* Use standard GSM characters.
* Limit emojis and special characters where possible, as they can increase cost.
* If you’re curious about credits, try an online SMS segment calculator to estimate usage.