When you look at a memory card, you will find a number on them indicating the class they belong to. Have you ever wondered what they mean? Simply put they define the card’s minimum sequential writing speed rating.

Most modern cameras and even phones possess the capacity to capture high definition videos and pictures which require faster write speeds, and this is where the speed ratings come into play.

Primarily, there are four different speed classes—10, 6, 4, and 2.

For some weird reason, the card’s naming scheme is a bit confusing (which I’ll come to in a bit). Class 10 rated cards being the fastest with 10MB/s minimum sequential writing speed (MSWS) it is suitable for ‘full HD video recording’ and ‘HD Stills consecutive recording’ and class 2 being the slowest of the lot but still being suitable for ‘standard definition-SD video recording’ comes in with 2MB/s MSWS.

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While class 4 and 6 come with their corresponding MSWS according to their class number like the others class 1 and 3 is where it becomes a bit confusing as they belong to a separate class and carry a different moniker known as the “UHS” or Ultra High-Speed cards they are capable of 10 MB/s and 30 MB/s MSWS capable of 1080P and 4K recording respectively.

As a bonus, they also support real-time broadcast capabilities unlike others on the list although these two are way more expensive and designed for professional use.

Which one should you buy?

Since you now know the difference between the various classes which one should you buy?

You’ll have to remember there is a price to performance ratio with all these cards and the more you move up on performance, the more you’ll end up paying for and unless you really can justify the need for speed there is really no point in going for the absolute fastest if you’re on a budget.

If you’re a professional or a hobbyist who does a lot of photography and videography and will be primarily using it on a DSLR which can take advantage of the card’s capacity, you should always prefer the faster UHS cards such as class 1 and 3. It would make your life a helluva lot easier to capture detailed images and videos and also transfer them faster to your workstation.

If you are planning to use the memory card primarily for storage of data such as photos, music, apps, and games on your phone or tablet, a class 4 or class 6 will suffice. If you don’t mind paying a premium for some speed, you can go for a class 10 card.

When you’re buying an SD card, you got to buy the right speed class, capacity for your needs. Although most modern devices are versatile with their compatibility, always check what your device supports and what speed and capacity you’ll realistically need.

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