Currently 16 of the 22 bits are allowed to be used, giving a maximum size of 32 GB.
C_SIZE This field is expanded to 22 bits and can indicate up to 2 TBytes (It is the same as the maximum memory space specified by a 32-bit block address.) This parameter is used to calculate the user data area capacity in the SD memory card (not include the protected area). The user data area capacity is calculated from C_SIZE as follows: memory capacity = (C_SIZE+1) * 512K byte As the maximum capacity of the Physical Layer Specification Version 2.00 is 32 GB, the upper 6 bits of this field shall be set to 0.