Since, presumably, the 140 character limit derives from SMS message limits, it might be interesting to look at what the message lengths are for these (note that this is GSM specific and I don't know the CDMA equivalents):<p>SMS payload is 140 octets. That means that you can store 140 8bit characters, eg Latin1 encoding, in a text message.<p>However, the GSM default encoding is 7bit packed. Each character is 7bit and they are packed together into the 140 octets, this leaves a maximum size of 160 characters per message.<p>For international characters, GSM uses USC2, which is a 16bit encoding, limiting messages to 70 characters.<p>You can also send concatenated messages, where multiple SMS messages make up the actual message text. In this case, you must subtract (from memory, so may be off) 4 octets from the limits, for the user data header. The user data header consists of a length and one or more information elements. An information element consists of 3 octets: an information element identifier (in this case, 0, for concatenated message) and some parameters (I'm not sure if this is specific to the IEI? I could look it up, but I'm too lazy.. for concatenated messages, the next octet is number of messages and the final one is the current message index).<p>Hopefully someone found this information interesting ;-)