Based on his personal observations and on analysis of the typical lengths of postcard and Telex messages, Hillebrand (The SMS concept developer) argued that 160 characters was sufficient to express most SMS messages succinctly.
Short messages can be encoded using a variety of alphabets: the default GSM 7-bit alphabet, the 8-bit data alphabet, and the 16-bit UCS-2 alphabet. Depending on which alphabet the subscriber has configured in the handset, this leads to the maximum individual short message sizes of
- 160 7-bit characters,
- 140 8-bit characters,
- 70 16-bit characters.
GSM 7-bit alphabet support is mandatory for GSM handsets and network elements, but characters in languages such as Arabic, Chinese, Korean, Japanese, or Cyrillic alphabet languages (e.g., Ukrainian, Serbian, Bulgarian, etc.) must be encoded using the 16-bit UCS-2 character encoding
Multipart or “long SMS” can be sent using multiple SMS messages, 6 to 8 segment messages are the practical maximum. So you can reliably send out up to 1,000 characters in a text. The Android phone will split the SMS message up every 160 characters (especially important if you have a link in your text).
The receiving handset is then responsible for reassembling the message and presenting it to the user as ONE LONG SMS MESSAGE.