Editing SD card (section)

===Storage capacity calculations===
The format of the Card-Specific Data (CSD) register changed between version 1 (SDSC) and version 2.0 (which defines SDHC and SDXC).

====Version 1====
In version 1 of the SD specification, capacities up to 2&nbsp;GB{{efn|name="GiB"}} are calculated by combining fields of the CSD as follows:

 Capacity = ('''C_SIZE''' + 1) × 2<sup>('''C_SIZE_MULT''' + '''READ_BL_LEN''' + 2)</sup>
 where
  0 ≤ '''C_SIZE''' ≤ 4095,
  0 ≤ '''C_SIZE_MULT''' ≤ 7,
  '''READ_BL_LEN''' is 9 (for 512 bytes/sector) or 10 (for 1024 bytes/sector)

Later versions state (at Section 4.3.2) that a 2&nbsp;GB SDSC card shall set its READ_BL_LEN (and WRITE_BL_LEN) to indicate 1,024 bytes, so that the above computation correctly reports the card's capacity, but that, for consistency, the host device shall not request (by CMD16) block lengths over 512&nbsp;B.<ref name="SDHCspec"/>

====Versions 2 and 3====
{{More citations needed|section|date=September 2023}}

In the definition of SDHC cards in version 2.0, the C_SIZE portion of the CSD is 22 bits and it indicates the memory size in multiples of 512&nbsp;KB (the C_SIZE_MULT field is removed and READ_BL_LEN is no longer used to compute capacity). Two bits that were formerly reserved now identify the card family: 0 is SDSC; 1 is SDHC or SDXC; 2 and 3 are reserved.<ref name="SDHCspec"/> Because of these redefinitions, older host devices do not correctly identify SDHC or SDXC cards nor their correct capacity.

* SDHC cards are restricted to reporting a capacity not over 32&nbsp;GB.{{citation needed|date=September 2023}}
* SDXC cards are allowed to use all 22 bits of the C_SIZE field. An SDHC card that did so (reported C_SIZE > 65,375 to indicate a capacity of over 32&nbsp;GB) would violate the specification. A host device that relied on C_SIZE rather than the specification to determine the card's maximum capacity might support such a card, but the card might fail in other SDHC-compatible host devices.{{citation needed|date=September 2023}}

Capacity is calculated thus:

 Capacity = ('''C_SIZE''' + 1) × 524288
 where for SDHC
  4112 ≤ '''C_SIZE''' ≤ 65375
  ≈2&nbsp;GB ≤ Capacity ≤ ≈32&nbsp;GB
 where for SDXC
  65535 ≤ '''C_SIZE'''
  ≈32&nbsp;GB ≤ Capacity ≤ 2&nbsp;TB{{citation needed|date=September 2023}}

Capacities above 4&nbsp;GB can only be achieved by following version 2.0 or later versions. In addition, capacities equal to 4&nbsp;GB must also do so to guarantee compatibility.{{citation needed|date=September 2023}}