For modern computing, at least since 1993, we have always 8 bits to a byte -> ISO/IEC 2382-1:1993
1 byte = 8 bits.
1 kilobyte (K / Kb) = 2^10 bytes = 1,024 bytes.
1 megabyte (M / MB) = 2^20 bytes = 1,048,576 bytes.
1 gigabyte (G / GB) = 2^30 bytes = 1,073,741,824 bytes.
In the last revised ISO/IEC 2382:2015 it didn't change to much:
--------------------------------------------------
2121333
byte
string that consists of a number of bits, treated as a unit, and usually representing a character or a part of a character
Note 1 to entry: The number of bits in a byte is fixed for a given data processing system.
Note 2 to entry: The number of bits in a byte is usually 8.
Note 3 to entry: byte: term and definition standardized by ISO/IEC [ISO/IEC 2382-1:1993; ISO/IEC 2382-4:1999].
Note 4 to entry: 01.02.09 (2382)
[SOURCE: ISO-IEC-2382-1 * 1993 * * * ]
---------------------------------------------------