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 (€) symbol, take the space of two characters.

When sending a Unicode SMS, the limit is generally 70 characters. Some non Western character sets, such as Arabic or Chinese, are always encoded as Unicode by your handset. Using non standard characters such as emoticons will also convert your SMS to Unicode.

When sending an SMS that contains binary data, the limit is 140 characters. Binary SMS messages are typically sent by your provider to configure your SIM card, for example. You will normally not receive them in your SMS inbox.

If an SMS message exceeds this limit, the mobile device will split it into multiple parts. Each part is billed as a single SMS by your SMS provider.