Ask LH: Does It Matter What Class Micro SD Card I Have In My Android Phone?

Ask LH: Does It Matter What Class Micro SD Card I Have In My Android Phone?

Dear Lifehacker, Can having a different class Micro SD card in my Android phone give any increase in performance? Signed, Memory BuffPhoto by Al

Dear Memory,

Micro SD cards, just like the larger cards before them, do have major differences in performance according to their class ratings, but that performance won’t necessarily be seen in certain situations.

For example: A DSLR that has the capability to fire off several shots a second will actually be noticeably faster if it has a higher class memory card, because the faster card allows the camera to save image data at a much higher rate than a slower card would. With the higher class card, the camera doesn’t have to pause and wait for its buffer to empty before taking more pictures, it just keeps shooting. The difference here is that your typical Android phone isn’t likely to put that big a load on the write capabilities of its memory card.

Most of the time that you spend waiting for a picture to be saved on a phone is usually the phone processing the image, not saving it.

A typical Android phone’s Micro SD card might be a Class 2, meaning it’s guaranteed to write at 2MB/s. Most companies actually make the cards to exceed that expectation, sometimes by quite a bit. If you take huge amounts of pictures with your phone, a Class 4 Micro SD card, which is just one class higher, might benefit you. It won’t exactly be a life-altering experience, but it could speed things up if your phone’s camera takes pictures at something higher than five megapixels. Most Android phones don’t do that.

If you use the USB Storage feature of your Android phone pretty frequently, then things are a bit different. When plugged into a computer as a USB storage device, the full capabilities of the card are used to transfer data — so the faster the card, the faster your data transfers. Most people might plug their phones in to do this once a month to switch out their music collection, so it’s no big deal. If you use your phone like this regularly, then the cost of a higher class card may be worth it.

Cheers, Lifehacker


  • The bit about the DSLR not having to wait to clear the buffer with a faster card isn’t right, either. It won’t have to wait *as long*, but if you fill the buffer, you’ve filled the buffer, and you will be waiting. For less time, agreed, and it does write out more quickly so (in some circumstances) it can avoid filling the buffer, but if you shoot fast enough to fill the buffer then you will have to wait. (I buy fast cards, but it doesn’t save me when I need to shoot long bursts.)

    • Get a better DSLR then. I know mine can with a class 10 shoot indefinitely in burst mode until the sd card is full. With a class 2 or 4 it fills the internal buffer quite fast and then you’re stuck waiting.

  • Theres actually a lot more to it than that from what I’ve learnt so far.

    Firstly, classes of SD card are dictated by WRITE speeds, not read. When used in a phone, writing doesn’t occur in huge amounts when compared to reads. In this case, I’ve actually heard its better to investigate further and invested in a well reviewed and tested brand name card of a lower class, rather buying a higher class cheaper made card. Its been said over at xda that in real world circumstances, a SanDisk class 4 SD card has been observed to out perform Kinston Class 8 SD cards of read speads.

    Adding to the above, this is especially the case if you’re using after-market hacks and scripts, such as apps2sd and data2ext. Both of these shift operating system data from the phones internal memory to the SD card. In this case, its far more important to have a phone that reads SD quickly, rather than one that writes quickly.

  • Doesn’t it depend on the hardware you’re dealing with as well? Even if your phone is writing enough data to warrant the higher throughput, doesn’t it depend if your card slot is SDHC compliant or not? Probably something worth checking on any of the cheaper smartphones, before wasting your money on a more expensive SD card.

  • From my experiences, even DSLR’s can never write at class 10 speeds, but retailers will tell you you need them. The reality is each model varies as class testing is sorta a trust game, and the nature of a mobile phone is to read more than it writes, so it’s not really useful anyway.

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