FAQ: Understanding MicroSD & MicroSDHC Card Speeds – Class 6 & Class 4 Cards? Write & Read Speeds?

sdassociation Shopping around for a new MicroSD card for your BlackBerry? Totally confused about what the difference is between a Class 4 and a Class 6 device? Wondering what 133x or 66x or 32x means?

Turns out that it is quite simple. The class defines the minimum write speed for a completely empty SD card. That means if you were writing to a new SD card that has never had any data on it how fast would it write.

  • Class 2 = 2 megabytes/second
  • Class 4 = 4 megabytes/second
  • Class 6 = 6 megabytes/second

So in short Class 6 is what you should be buying for fast write speeds. On top of this there is also the speed rating of the card itself. This is based on how fast the microSD card can READ the data off the card. You will see this usually described as 32x, or 66x, or 133x, or something with an x and the end. :)

These measurements are based on the original CD-ROM drives which could write 150kb/second. So 32x means 32 multiplied by 150kb/second or 4.8MB/second. This nice little table from Wikipedia gives you a basic idea of what each one stands for in terms of speed:

Rating Speed (MB/s)
6x 0.9
32x 4.8
40x 6.0
66x 10.0
100x 15.0
133x 20.0
150x 22.5
200x 30.0

Let me know if you have any more questions!

6 total comments on this postSubmit your comment!
  1. Thanks for the detailed info. I have an 8gb card in my Curve 8330. I don’t think a faster writing card would help. The curve still needs a faster processor :(

  2. What the different between SD and SDHC in relation to the read and write speed of those microSD card?

  3. I just read about this a week or so ago on Wikipedia, Here’s some more info http://en.wikipedia.org/wiki/Secure_Digital_card

  4. Right, but which Blackberry smart phones are capable of which Class is the question. If the device is only able to write at 2, spending the extra for a 4 or 6 is a waste, no?
    Given price parity, of course just buy the faster. But it would be nice if RIM would upgrade their capacity FAQ by adding max write speed each hardware supports.

    And don’t forget the new SDXC if you’re gonna write about cards!

Latest Articles from

AndroidEffect - Improving Android One Tip at a Time

BlackBerry© is a registered Trademark of BlackBerry Limited. BerryReview is in no way affiliated with BlackBerry Limited though sometimes their lawyers send us love letters...

Copyright © 2007-‘2014’ BerryReview LLC