Memory Card- its Classes and Speed Capacities how to choose an SD card

What is Memory Card – All Different Speed Class and Capacities

Memory Card- its classes and speed CapacitiesHello friends in the last article I explained you about the memory cards and its types. And now I am going to tell you about their class and speed range. Presently there are several types available in the market, but the biggest problem is which one to purchase  because there are so many varieties coming in the market depending upon their Class & Bus Interface.

This could be little confusing if you don’t know what do they mean.

Each memory card was marked with some special symbols, and most people who do not know its meaning cannot decide what to take. So here I will explain you about all the classes, bus interface and speed range of the memory cards available in the market.

Types of Class

There are four different speed class:

  1. Class 2: This class has writing speed of 2 MBps and suitable for Standard video recording.
  2. Class 4: Its writing speed of 4 MBps and suitable for High Definition video (HD) recording including Full HD (from 720p to 1080p).
  3. Class 6: This has 6 MBps writing speed, comes in ‘V6’ Video speed class and suitable for High Definition video (HD) recording including Full HD (from 720p to 1080p).
  4. Class 10: This has 10 MBps writing speed, comes in ‘V10’ Video speed class and suitable for Full HD (1080p) video recording and consecutive recording of HD stills, real-time broadcasts and large HD Video files (UHS bus, Classes U1).

All these classes are described in the following tables:


Previously the storage of 1 GB, 512 MB, 256 MB and even 128 MB sized memory cards were also available but now they had become almost obsolete. Today we have a vast range of size (2 GB to 2 TB). The available sizes are 2 GB, 4 GB, 8 GB, 16 GB, 32 GB, 64 GB, 128 GB, 256 GB, 512 GB, 1 TB and 2 TB. All you need to know is that the compatible size for your device. The read and write (r/w) speed of a memory card is also an important thing to consider while purchasing. It is responsible to fetch data from the memory card and to write the data on it. No matter how big size memory card you have without a good r/w speed it’s worthless. That is why these days SDHC and SDXC with Class 10 types are mos preferred and most suitable for a common man.


Now you have all the brief idea regarding the memory cards about their features and applications and also the basic things to be considered while choosing the best suitable memory card for your device. This may vary person to person depending on their needs and what device they are carrying. So I hope from now onwards, you won’t confuse what A1, A2, U1, U3, C4, C6, C10, I, II & III mean and what are their speed ranges. I hope this article helps you to make your decision to what memory card you should buy. Thanks for your time.


Question 1. What is class 10 in SD card?

Answer: Class 10 is the speed class rating for the standardization of data transfer speeds. SD Card Association (SDA) has established this speed class rating which is a minimum sequential writes speed for a memory cards.

Question 2. What is the fastest SD card class?

Answer: Ultra High Speed (UHS) classes are the fastest SD card class. They are usually needed for the 4K capable video devices which needs faster write speeds.

Quesiton 3. What is v30 on SD card?

Answer: The SD Association (SDA) has introduced a Video Speed Class rating, designed to identify cards capable of 8K, 4K, 3D and 360° video capture. The speed class, which guarantees minimum sustained performance, comprises five ratings: V6 (6MB/sec), V10 (10MB/sec), V30 (30MB/sec), V60 (60MB/sec) and V90 (90MB/sec).

Question 4. What is the difference Class 10 and UHS 1 memory card?

Answer: They are identical in their technical specifications and there is no difference in the data transfer speeds of Class 10 and UHS 1. Both memory cards have 10MB/s of minimum data transfer speed.

Question 5. Can I use SDXC instead of SDHC on my host device?

Answer: Yes, only if your host device compatible to SDXC cards. Because SDXC uses a different file system called exFAT which is not compatible with host devices and work differently than SD and SDHC.