Maximum Length Of English
The maximum length of text message that you can send is 765 characters. However, if you send more than 160 characters then your message will be broken down in to chunks of 153 characters before being sent to the recipients handset.
(1 part = 1 SMS , 2 Parts =2 SMS till 5 parts = 5 SMS .
"5 parts * 153 char= 765 char")
The good news is that the vast majority of handsets nowadays will join the multiple message parts together and present a single, extra-length message for the recipient to view.
The bad news is that the networks will charge you for every chunk of 153 characters that you send!