According to Wikipedia, an SMS message is always exactly 1120 bits, and as for encodings...
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
UTF-16 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, or 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.
Russian, Serbian, Bulgarian, etc.) must be encoded using the 16-bit
UTF-16 character encoding.