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SD Card Overview

SD SDHC SDXC
SD SDHC SDXC
1MB - 4GB 4GB - 32GB 32GB - 2TB (theoretical)
FAT12 / FAT16 FAT32 exFAT

Speed Class Rating

  • Official unit of speed measurement, defined by SD Association.
  • Measures minimum write speeds.
  • Readable by devices; they can warn the user if the inserted card's rating falls below minimum requirement.

x-Rating

  • Unit of measurement derived from standard 1.2Mbit/s CD-ROM drive speed.
  • e.g. basic cards up to six times (6x) standard CD-ROM data rate (7.2Mbits v 1.2Mbits).
  • Some manufacturers use maximum read speed as x-rating (read speeds typically faster than write speeds).

Class Definitions

  • Important to differentiate the difference between Megabits (Mb) and MegaBytes (MB).
  • 8Mb = 1MB.
Class Rating Min. Transfer Speed Applications Available Card Types
2 13x 16Mbits/s
(2Mbytes/s)		 SD video recording SD / miniSD / microSD
SDHC / miniSDHC / microSDHC
SDXC / microSDXC
4 26x 32Mbits/s
(4Mbytes/s)		 HD (720p) video recording
6 40x 48Mbits/s
(6MBytes/s)		 HD (720p) video recording
10 66x 80Mbits/s
(10MBytes/s)		 Full HD (1080p) video recording
HD still consecutive recording
UHS Class Rating Min. Transfer Speed Applications Available Card Types
UHS 1 333x 400Mbits/s
(50Mbytes/s)		 Full higher potential of recording real-time broadcasts and capturing large-size HD videos SDHC UHS-I
SDXC UHS-I