How many characters can be used in an SMS message?
This depends on a couple of things:
If you are sending a normal text SMS it will generally be 160 characters. Some special characters, like the Euro (€) character will take the space of 2 characters.
When sending a Unicode SMS this will generally be 70 characters. Some non-western character sets like the Arabic or the Chinese character set will always be Unicode encoded by your handset. Using non-standard character like emoticons will also convert your SMS to Unicode.
When sending an SMS that contains binary data the limit is 140 characters. Binary SMS messages may be sent by your provider to setup your SIM card for instance.You will normally not receive them in your SMS inbox.
If an SMS message exceeds this number of characters the mobile will split it up into multiple parts. Every part is billed as a single SMS by your SMS provider.