That’s because SMS has a 1120 bit message capacity and uses one of two encoding mechanisms. GSM-7 uses 7 bits per character and a correspondingly limited chara

That’s because SMS has a 1120 bit message capacity and uses one of two encoding mechanisms. GSM-7 uses 7 bits per character and a correspondingly limited character set that allows for 1120/7 = 160 characters. UCS-2/UTF-16 uses 16 bits per character for a total of 1120/16 = 70 characters per message.