SD and microSD Memory Cards Class Rating


What is the meaning of the Class rating on SD and MicroSD cards?

The Class rating on memory cards refers to the SD Association specification and references the minimum write speed the card is guaranteed to support.


 Class 4 4 Mbytes/second
 Class 6 6 Mbytes/second
 Class 1010 Mbytes/second 


 The speed rating is primarily of interest in video recording.  The card should be able to support the minimum recording speed of the video device.  A good discussion of recording speeds, including the UHS-I Class can be found at this SD Association link.