How To Choose The Right SD Card For The Job

icon2   How To Choose The Right SD Card For The JobSD cards are the most common form of removable data storage for portable devices that we have to date. However, many people have had situations where they put the card in their device, and it does not read. Other times, it fails to record. Often, it always ends with the person saying, “Well, I thought I had enough storage!”

But that’s just it – SD cards aren’t all about storage! In fact, there are several other factors to consider, and when purchasing your cards, you should make yourself aware of them. That said, SD cards aren’t all created equal, and it’s important to be educated as to what separates each one from the rest.

As a given, all types of data are different, and although I can’t tell you exactly what to buy since I don’t know your device, I can supply you with the proper information to make that decision on your own.

The Elements

When purchasing a SD card, you should take into consideration four main factors. Granted, your manual (you know, that thing you tossed in the trash as soon as you unboxed your device) may actually have recommendations as to what kind of card you should get. Even still, it’s good to know about them:

  • Class
  • “X” Rating
  • Storage
  • Size

There are four different SD card classes that you can buy. You can grab a Class 2, a Class 4, a Class 6, or a Class 10. This class number simply lets you know the minimum write speed of the card. But what is that number? Well, that’s easy. The number of the card denotes the minimum MB/s that the card can write. For instance, a Class 2 writes at 2 MB/s. Furthermore, there are even ultra-high speed (UHS) cards which can transfer anywhere between 50 MB/s to even 312 MB/s and up.

The “x” rating (or x speed) is actually just how many times faster the card writes down information compared to a standard CD-ROM drive. As a note, these drives write data at about 150kB/s (or 1.23Mb/s). For your information, a Class 2 card has an “x” rating of 13x. Why? Well, I prefer to do this math with megabits, but we can see that 13 times 1.23Mb equals 15.99Mb. Since 8 megabits equals a megabyte, divide the 15.99 by 8, and we get about 2MB. Thus, this is a Class 2 with a 13x rating. (I hope that made sense.)

As a note, some cards will blatantly display the “x” rating and some won’t. Ultimately, you just need to focus on the MB/s. Classes and “x” ratings are just easier ways of explaining it.

classx21   How To Choose The Right SD Card For The Job

As far as storage goes, this is just based on the type of media you are wanting to hold. What I would suggest is checking out the average size of each bit of media you are recording (everything is different), and then you’ll be able to determine roughly what you need. However, there are currently three primary types of cards with different capacities:

  • SD – Not used as often; can hold up to 2GB
  • SDHC – The upgrade to the original SD (a.k.a. SD 2.0); can hold up to 32GB
  • SDXC – The upgrade to the SDXC; can hold up to 2TB

cards2   How To Choose The Right SD Card For The Job


Moving right along, there are actually three different sizes of SD cards that you can choose from:

  • Standard size (32mm x 24mm)
  • Mini size (31.5mm x 20mm)
  • Micro size (11mm x 15mm)

Each of these pertain to the device, and you should be able to tell anyway. Smartphones may use smaller SD cards than cameras, but they are still SD cards, nonetheless.

sizes   How To Choose The Right SD Card For The Job


Which Card Is Right For You?

SanDiskSDHC front 8GB hires1   How To Choose The Right SD Card For The Job

For photos, I would recommend focusing primarily on the storage (but not just that). If you’re shooting snapshots with your Nikon Coolpix, you could get away with something in the zone of 4 to 8 gigs. However, when it comes to hi-res RAW images, you have little more to worry about. Let’s take a slightly closer look at card specs for your devices.

Let’s hypothetically say an average RAW image for my camera is about 25MB. Well, considering there are about 1000 megabytes in a gigabyte, that would mean my 16 gigabyte card can hold about 650 RAW images. Of course, this could always vary. Do the same math with your point-and-shoots, and this should help. As for speed, pay attention to the recommended Class Rating and “x” rating.

lexarvideo   How To Choose The Right SD Card For The Job

For video, the SD Association (yeah, that exists) actually has a few recommendations. Here they are:

  • Class 2 – SD Recording
  • Class 4, 6 – Full HD Recording
  • Class 10 – Full HD Recording and HD Still Consecutive Recording

In theory, this should work. However, once again, these are just the minimum requirements. If the camera actually requires a higher “x” rating, then you would be better off purchasing a higher quality card. For instance, if you put a 40x card in a device that requires 50x, the card won’t be able to function properly.

Ultra microSDHC UHS I U1 16GB HR1 590x484   How To Choose The Right SD Card For The Job

For smartphones and tablets, you’ll find yourself looking at the same information. You simply need to know the rate which data is written to the card, and you also should know about how much data you need to store.

All in all, I’d say data usage varies quite a bit, and it’s hard to pinpoint every single device. Now that you know what to look for in a card, you can apply this information to your own toys.

Which Card Will You Buy?

This is a good rundown of what to look for in your next SD card purchase. Much like when looking to purchase a car, it’s good to know what exactly that each bit of data means so you can make an educated decision. Ultimately, you should be able to get a feel for what’s good for you.

For more articles about memory card and selection, you should check these out:

What kind of card will you buy? What devices do you have that utilize SD memory cards?

Image Credit: JusbenWikipedia

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Ashwin Ramesh

Very informative article, Joshua! I’ll make sure I buy the right SD card the next time I plan to buy one :)

Joshua Lockhart

Thanks, Ashwin. Buy me a few extra ones, too. Alright?


I try to minimize the number of storage formats (sometimes a losing battle) — and for now, it’s microSD card, Class 10. I find it the most versatile — and also because it seems to be “the format” for cell phones.

The same MicroSD card — by itself or coupled with a SD card adapter or a USB adapter — can be used in my phone, cameras, MP3 player, tablet, laptop and desktop.


Oops… I meant MicroSDHC cards.

Kishore Kumar

now every one knows differences between sd card types.. most informative site..

Douglas Mutay

I just find that I have always use SD card without taking care of these info. I have looked at some of the SD I have and some of them doesn’t even give any of these info. I can assume they are pirated one…

Joshua Lockhart

Pirated ones? Do you have pictures?

Douglas Mutay

Yes I do but can’t post it here…

Âdil Farôôq

Wow i always had different types of SD cards but never knew that information about it i just looked for the Storage size and purchased. Thanks for this useful information really worth reading and informative.

Joshua Lockhart

I’m glad that the article helped!


I only look at Card size and did really bother about the details. Very useful information. I guess little details overlooked seemed to be missed while we only wonder what they really mean.

susendeep dutta

This article is very useful for knowing SD cards in detail.

Well,in many forums,I had seen that Android smartphones(especially the mid-range ones) becomes unstable if Class 10 cards are used in place of Class 4.
Does it implies that only high end Android phones are made to use Class 10 SD cards?
If yes,do you agree with using Class 6 SD cards in mid-range phones?

Joshua Lockhart

I’m not entirely sure! It really has to do with the individual phone.

If the phone recommends a Class 4, I might want to just use that. Why? Well, since the Class 10 refers to minimum, it might go beyond (or close to) the maximum speed of that phone.

Chew Jian Yue

Highly useful article, which I might consider on, as I want to buy a SD card for my DSLR (Nikon)…

Joshua Lockhart

I don’t know about Nikon, but I use Class 10 cards with my Canon. They say you can use a Class 6, though.


Great article I didn’t know there were so many different types of cards! I’m now very informed.


Joshua Lockhart

: ) Glad I could help.


I really wish you should have posted this article much earlier.

Joshua Lockhart

I’ll take care of that when MakeUseOf has a giveaway review for the first time machine.


The Class-2 SD cards are now difficult to get. I have found that the Class-4 cards are good workhorse devices for saving stuff like documents. I would not buy a higher speed card unless I could confirm that it was needed because they tend to be more expensive. (That being said it seems that Amazon has no order whatsoever to their pricing!). How do you know for sure if you need a faster card than you are using? That is difficult because it seems that even the manufacturers get it wrong. For example HTC recommends a Class-2 SD for its Desire S. But even a Class-4 seems to be inadequate for the phone’s HD video camera.

Félix S. De Jesús

Very good article. The only problem is the price.

Joshua Lockhart

You’re tellin’ me…

Félix S. De Jesús

My internet service is bad… I said, the problem is the price of any card, specially with the XC Technology hehehe…

Walter Gilbert

Thank you for this information. I will more attention in selecting cards from now on.


Well it pisses me off not to have been made aware of this before by either the card makers or the camera makers

Joshua Lockhart

I think it’s just something you have to figure out on your own, I guess. Take lenses for instance. You have to figure out which lens is best for your camera, right? (That may have been a horrible analogy – bear with me.)

Nohl Lyons

Great reference article

Igor Rizvi?

Oh i love how you teach us everytime soemthing new and very interesting..thanks alot! I have to admit,i didnt even take anotice of those marks when iwas buying an sd card! :)

Joshua Lockhart

I’m glad you liked the article, Igor! Hopefully, it will help you when buying your next card.

James Cameron

Thank you for the article, it certainly provides some useful information. One of your graphics points to the UHS-1 label on the card, but your article does not appear to discuss this. Can you please provide some information as to how to use that piece of information as well.

Joshua Lockhart

Hey James. I didn’t touch on that very much, but I suppose I could have.

UHS stands for for “ultra-high speed”, and as you can tell… they go super fast. Personally, I didn’t realize how common UHS was, so I was thinking that the article would apply more to practical consumer devices. Granted, I’ve discovered it’s a bit more common than I realized.

UHS-I transfers at least 50 MB/s and when classified as a UHS104, can go up to 104 MB/s. UHS-II goes up to 312 MB/s.


This is super helpful! I’ve always wondered about all the options but never taken the time to research it. I guess I better go check what I have in my DSLR camera. Thanks for taking the time to explain all this.

Totoy Badiola

Cool! Thank you very much. It was very informative, indeed.

Nevzat Akkaya

Very well written article, thanks. I always try to reach the technical details when buying gadgets, however it is not so easy always. Sellers try to hide them when they do a promotion of an old tech hardware. We should always be careful.

Priyank Vijaywargi

Excellent article!!

Lisa Santika Onggrid

Thanks, I’m not aware of class differences.

Ahmed Musani

great information Sir. really really helpful. thanks a lot


I wish I had come here before to have a look at this piece of informtion. But, I won’t make the same mistake again

Tom Cruz

This is really very informative. Thank you so much for being so helpful to others. Love this post.

Debbie Franklin

Wow! That’s really cool info, I will totally use this. Thanks

Aibek Esengulov

just bought myself a tablet and wasn’t sure which SD card to buy. This post helps)

Joshua Lockhart

Thanks, Aibek!

Ayan Panja

very much helpful document. but some times I could not find any class to a card. is this a sign of duplicate SD card?