What are SD Card Class differences?

The other day, a friend of mine asked me about SD (Secure Digital) memory card class differences. My friend told me that while she looked around eBay for deals on a 32GB SDHC card for her recently purchased GoPro, she noticed that the SD cards were classified by class numbers, something she did not realize until recently. She asked which she should get… I told her the higher the number the better.  I thought I’d share this little info about SD class types with all of you…

SanDisk 32GB Class 4

So what defines a class and why does it matter?

The class number of an SD card, defines the speed class rating of a card.

The lowest class is Class 2 and the highest being a Class 10.

Here are the writing and reading speeds of each classes in its respective order.

Class           Speed

Class 2       2 MB/s

Class 4       4 MB/s

Class 6       6 MB/s

Class 10    10 MB/s

Notice that the Class number is identical to the speed it runs on. So if you have a class 10, you have a reading and writing speed of 10MB/s.

So does it really matter?

Yes! It is like comparing 2 cars; one that runs on 2 miles per gallon of gas compared to another car running on 10 miles per gallon. You want to know which is more convenient and efficient for your purpose.

In addition, this is what makes a Class 4 or higher more expensive than a Class 2.  A Class 2 is definitely cheaper than a class 10 but the class 2 SD card is slower and as a result can slow down the data transfer speed from your camera to your memory card.

For many great cameras such as the GoPro HD video cam, GoPro recommends that you use a brand name SD card with at least a class 4 as pictured above. On the GoPro website, they sell Sandisk Class 4 SDHC cards but you should check other brands as well. SanDisk is a big name brand, but so is Kingston, Transcend, Panasonice and many others. I recommend brand name cards simply because of the fact that I need something that won’t fail on me on the field. Although there are cheap cards out there for really great prices, I tend to still go for the brands because I did have an experience with a generic brand that failed on me!!! I guess with almost everything that spans around common consumer logic, you get what you pay for.


Transcend 32GB Class 10
Transcend 32GB Class 10

I personally use a 32GB Class 10 Transcend SD Cardfor my GoPro HD cam and it has never failed on me. I like Transcend because they have a lifetime warranty on all their memory products, which means they put that much confidence in their quality and products.The warranty is no bullshit either because it did come in handy when one of my Transcend RAM memory chips in my computer failed 2 years after purchase. They replaced it as soon as I sent them my defective RAM chip.  The only thing you pay for is the shipping… but for something small and light like an sd card, it’s so cheap, I didn’t mind paying for the shipping for a brand new memory card!

Anyway back to the point… I have no complaints about using a class 10 sd card. Some may say that it is overkill but it definitely doesn’t cause any lags on my camera or delays when transferring data to my computer.

Also, there were several times when my class 10 32 GB card became full HD videos and I was pretty amazed when all of it was transferred into my computer within 25 minutes while using a card reader. Compare that to a  Class 2 card that takes literally several hours!!!

Save your time and save some cents on your power bill by getting a faster card. It’s worth it.

Just a note… for good deals, buy online especially on eBay. I can definitely guarantee that it is so much cheaper than buying at a local retail store.

*I use affiliate links at no cost to you. If you choose to make a purchase through my link I make a small commission. Thank you for trusting my recommendations!

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