A common question that I get asked is which SD cards are worth purchasing and which aren’t? There are several things to take into consideration and price is always a factor too. But is it worth spending the extra money on one with all the bells and whistles or will that money go to waste. Which SD card should I buy?

Speed Class

SD cards are classified by speed. There are four different speeds that SD cards come in: 10, 8, 4 and 2. As you’d imagine, 10 is the fastest of these four speed classes and 2 is the slowest. We’ll not go into the complicated read/write speeds of each here, but the speed classes do suit different devices. An SD card with a class 10 speed will be suitable for any device, but 8 will be enough for other devices, as will 4 and 2.

Here is the rule of thumb when it comes to which speed class you need.

Speed Class 2

Speed class 2 is suitable for taking still photos.

Speed Class 4

Speed class 4 is suitable for taking still photos or low-resolution video.

Speed Class 8

Speed class 8 is suitable for taking 720p video (HD) and HD still photos.

Speed Class 10

Speed class 10 is suitable for taking 1080p video (Full HD). This class is also suitable for taking photos in “burst” mode where several still photos are taken per second.

UHS Speed Classes

As well as the above speed classes there are also two other speed classes referred to as UHS (Ultra High Speed). SD cards which have a UHS speed class are more suited to professionals so the chance of you needing to purchase one is pretty slim. Also, the price of UHS SD cards is significantly higher than that of a regular SD card. The two UHS speed classes are UHS-I and UHS-II (with the latter being the faster).

SD Card Size

The next thing to consider when buying an SD card is the size of it. Currently you can get a standard sized SD card, a mini-SD card or a micro-SD card. You’ll generally find a full sized SD card will fit your camera or video camera and a mini or micro SD card will fit your phone.

It’s always worth checking which size of card your device will take. With a standard sized SD card there will be no way of putting this into a device that only takes micro-SD cards, but if you went for a micro-SD card you can place it into an adapter to get it to work in a full sized SD card slot.


The capacity of an SD card is another important factor. Generally, the more storage the better, but only buy what you actually need. An important point to note here is that some devices will only support SD cards up to a certain size, so before buying a 32GB card you should make sure that the device you want to use it with will support cards of this size.

The capacity of the cards will also vary depending on the type of SD card. Yes, this is another factor that you need to think about. Standard SD cards (SDSC) generally have a capacity up to 2GB in size. The next generation of SD cards, SDHC, have a size between 2GB and 32GB in size. The third generation of SD cards, SDXC, offer a capacity of 32GB to 2TB. Bear in mind that certain devices will only support certain types of SD card too – SDXC is the newest of these three formats and it offers the largest amount of storage but fewer devices will support these types of cards because of this.


So, when buying an SD card remember to take the following into consideration:

  • Speed Class (10, 8, 4, 2)
  • Type (SDSC, SDHC, SDXC)
  • Capacity
  • Size (Standard SD, Mini-SD, Micro-SD)

If you need an SD card for a full HD video camera then don’t be silly and buy a 2GB SDSC class 2 mini-SD card. Go for a class 10 SD card that is full sized with as much storage as you require and remember to check the manufacturer’s specifications for your camera’s model to ensure that the card you want to use will be suitable. Better still, take your camera and the manual along to the shops with you so you don’t make any mistakes.

Image Credit: James West

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Test analyst by day, blogger by night. Michael is an avid geek, hence his creation of this site. He has a serious Internet addiction.