A: When you send an SMS message containing more than 160 characters, the message is split into smaller messages for transmission. Large messages are split into 153-character "segments" and sent individually, then re-assembled by the recipient's device. The effective character limit per segment is 153 rather than 160, because a data header must be included with each segment to ensure correct re-assembly.

For example, a 161-character message will be sent as two messages: one with 153 characters and a second with eight characters.

If you include non-GSM-7 characters, such as Chinese script or emoji, in SMS messages, those messages have to be sent using the UCS-2 encoding. Messages containing one or more UCS-2 characters can contain up to 70 characters in a single, non-segmented message. UCS-2 messages of more than 70 characters will be split into 67-character segments.

The max size of one SMS is 10 message segments, so it is 1530 or 670, based on whether it has Unicode characters.