Memory Cards Speed Class

In 2006 the SD Card Association defined a categorization according to the minimum writing speed called Class

 

Classification of cards according to their writing speed
Class 2 4 6 10
Minimum write rate (Mo/s) 2 4 6 10

 

UHS (Ultra High Speed)

 

In addition to these classes, there are the UHS-I (Ultra High Speed I) specifications, whose RAM technologies used allow a higher theoretical average throughput, depending on the device using the card.

The second version of this UHS-II standard (November 2013) further increases the average theoretical throughput. adding a second row of pins to the card.

 

Pin Layout Pin layout 1 Pin layout 2
SD Bus Interface Hight Speed UHS-I
Hight Speed
UHS-II
UHS-I
Hight Speed
UHS-III
UHS-II
UHS-I
Hight Speed
2TB
(exFAT)
SDXC SDXC 1 SDXC 2 SDXC 3
32GB
(FAT32)
SDHC SDHC 1 SDHC 2 SDHC 3
2GB
(FAT12/16)
SD      
  25MB/s 104MB/s 312MB/s 624MB/s

 

 

Speed Classes

Minimum Sequential Write Speed according to the logo(s)
Minimum Sequential Write Speed Speed Classes
Speed Class UHS Speed Class Video Speed Class
90 MB/sec     V90
60 MB/sec     V60
30 MB/sec   UHS Class 3 V30
10 MB/sec Class 10 UHS Class 1 V10
6 MB/sec Class 6   V6
4 MB/sec Class 4    
2 MB/sec Class 2