Typically 1 SMS can contain around 160 characters. Special characters and message headers may take up additional counts. Messages with one or more non-GSM characters have to be sent using UCS-2 encoding and can only contain 67 characters per segment for multi-part messages.
When you compose an SMS message, our portal will let you know how many SMS will need to be sent. This will be the most accurate way to understand the numbers.
As part of the SMPP specifications, we must split up the messages to send when we receive a request that includes more than 160 characters. They will then be reassembled into a single message on most handsets.