A multipart SMS is formed from several standard SMS containing a 7-byte header at the beginning of each one. Since this 7-byte header is within the message, it reduces the total size of each SMS to 153 characters each.
SMS Maximum Lengths
- A single SMS offers a 160 character length.
- Two SMSes will provide a total of 306 characters.
- Three SMSes will provide a total of 459 characters.
These numbers will be lower if you use emojis, due to code being added to enable emoji support.
Also worth noting, phones which support latin based languages such as English, use the GSM alphabet. Some characters in the GSM alphabet require 2 characters because they are extended alphabet characters. These extended characters are taken into consideration when deciding how to split the message into different parts. The full GSM character list can be found here.
Most modern smartphones will render these SMS as one block, however, if the SMS is received by older handsets the parts may come through as separate messages.
A multipart SMS is billed by the number of individual SMS messages used. For example, if you send a 459 character message, you will be charged for 3 SMS.
All the work to split up the messages into smaller segments will be done automatically for you. However, to find out more about our multipart SMS feature, or how this will affect your billing, contact our customer success team.