SMS Character Sets

When you want to send an SMS message, whether by itself or as part of a structured SMS or iSMS activity, you'll need to understand that there are two different sets of characters that are used by different mobile carriers:

1 - GSM

Many mobile networks limit text messages to the 128 character GSM character set (full list here).  When using this set, a text message can contain 160 characters. This means there can be 160 characters in an SMS.

There are also 10 "extended GSM" characters, which use two 7-bit characters (ESC followed by another character). An example is the Euro symbol: €.   If you use any extended GSM characters, it will take up two, not one, of the 160 character limit.

2 - UCS2

If you need to send characters that aren't in the GSM character set, you'll need to use UCS-2 character set.  UCS-2 allows you to send most common characters that you could type on your computer (which uses unicode character set), but each UCS-2 character takes up twice as much memory as a GSM character. That means that if you use any UCS-2 characters (full list here), your text message can only include 70 characters, not 160.

SMS Message Length Calculator

If you're not sure which character set you're using, and want to know the exact length of any of your messages, paste them into this calculator.