Technology Explained

How to Pick & Buy the Best SD Card for Your Needs

Andy Betts 23-02-2016

The SD card is an integral part of digital life. So many devices we use on a daily basis require them for one purpose or another, but the card that’s right for one device isn’t always right for another.


In this article we’ll take a look at some common, practical uses for SD cards and show you how to make sure you always buy the optimal one for any given activity.

Important SD Card Basics

Before we proceed, you might want to check these mistakes to avoid when buying a microSD card 5 Mistakes to Avoid When Buying a MicroSD Card Buying MicroSD cards may seem simple, but here are a few critical mistakes to avoid if you don't want to regret your purchase. Read More as it clarifies a few facts and common misconceptions. The main points to be aware of include:

  • SD vs. MicroSD. These two types of card are identical insofar as they use the same standards, and all microSD cards come with an adapter that enables them to fit into a full SD card slot. However, the write speeds of full-sized cards do tend to be faster than the speeds of their micro-sized counterparts.
  • Speed Classes. A card’s speed class –such as Class 6 or U3 — indicates the minimum write speed of a card. This is one important element when identifying cards that are suitable for the task at hand, but it won’t tell you which card is the fastest. You also need to ensure your hardware is compatible with a particular speed class (e.g. UHS-II cards have a different pin layout to older cards).
  • Beware of Fakes. You should always buy your SD cards from reputable sellers, and preferably in their original packaging, not a “frustration-free” option. There are lots of fakes on the market.

SD Cards for Photography

If you own a camera, then you will need at least one SD card to store your pictures on. The speed and size that’s best for you depends on the type of camera you’re using Not Everyone Needs a DSLR: Which Camera Is Right for You? Some people say you can't take good pictures without a DSLR camera. They're unequivocally wrong. Here's our guide to which type of camera you should buy. Read More . And the speed isn’t just a factor in how fast the camera will save your images, but how quickly it will copy them over to your PC’s hard drive.


Casual Photography

For casual photography — using a point-and-shoot camera and shooting in JPEG format — the capacity of the card you choose is more important than the speed. Compact cameras are not known for their fast shot-to-shot time, and with images in the region of 5 MB, your SD card is unlikely to ever be a performance bottleneck.


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The biggest consideration is whether you should use a single card with a lot of storage capacity or multiple cards that have smaller capacities each.

If you’re traveling or shooting special occasions, you should definitely consider the latter option. If a card fails when you’re only using one, then all of your images will be gone. If you’re rotating between four cards, you’ll only lose a quarter of your images if one of them happens to fail.

Serious Photography

If you’re a more serious photographer who’s shooting with serious equipment — DSLRs, high-end mirrorless cameras, or even an enthusiast-class compact camera — then you should consider both speed and capacity when picking an SD card.



RAW images are much bigger than JPEG images Budding Photographer? Here's Why You Should Be Shooting Raw Every dSLR, prosumer and even some high-end compact cameras have the ability to save raw image files. This isn't just a higher quality of image, it's a gift from the photography gods. Read More , meaning they’ll typically be somewhere between 20 to 40 MB per image — and can be even bigger depending on your camera. For example, uncompressed RAWs on the Sony A7R II are over 80 MB each.

Factor in the faster shot refresh times, along with burst modes that can rattle off multiple shots per second, and you’re going to be writing a lot of data to your card in a short space of time.

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As a result, you should look to get the fastest card your camera supports, which ideally means UHS Speed Class 3 (with U3 printed on the card) or better. The SanDisk Extreme Pro cards are very well regarded for this.

These cards will be large enough to handle the bigger file sizes, too, although you might still want to split your images across at least a couple of different cards to protect against failure.

SD Cards for Videography

All modern consumer video cameras use SD cards, and getting the right one is very important. Use one that is too small and you’ll limit the length of time you can shoot for, and use one that is too slow and you’ll risk dropping frames as the card cannot write the video data fast enough.

The quality of the video you shoot varies based on a combination of several settings, including resolution, bitrate, frame rate, and file format. Using a simple formula, you can use the bitrate to determine what speed of SD card you need.


Bitrate is the amount of data that is written to the card and is normally measured in Megabits per second (Mbps). We know that in computing there are eight bits in a byte, so if you divide the Mbps value by eight, you can convert it into Megabytes per second (MBps). You can then use this value to ensure your chosen card is fast enough.

Action Video Cameras

If you’re using an action camera Buying a GoPro or Action Camera: 7 Useful Things You Need To Know If you're into skiing, cycling or surfing, then an action camera is the perfect way to record your adventures. Read More like the GoPro HERO4 Black at its maximum bitrate of 60 Mbps, that equates to 7.5 MBps using the simple formula above. As long as your SD card is equal to or faster than this, it should be okay.


Class 10 and UHS-I cards have a minimum write speed of 10 MBps, so that’s what you should aim for at the very least. Also, 7.5 Megabytes per second amounts to 27 Gigabytes per hour, so you will be able to record for around 70 minutes on a 32 GB card.

Serious Video Cameras

The above formula applies regardless of the resolution you’re shooting at. However, 4K needs a high bitrate to maintain its quality, while lower resolutions are much more forgiving of lower bitrates. In high-end video cameras, 4K video files will often be much larger than 1080p files.

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As a result, there’s a general rule of thumb for buying SD cards for video: at minimum, you need at least Class 6 for 720p, U1 for 1080p, and U3 for 4k.

Dash Cams

The main exception to the rule is if you’re buying an SD card to use in a dash cam How to Choose the Right Dashcam for Your Car As you browse dashcams you may wonder why one would be desirable. What features do they offer? How are they different from a regular camera? Why not just use a smartphone? Read More  or any other kind of security camera. Here, length of recording takes precedent over quality, so the bitrates fare often lower.

Again, you should check the speed to ensure you pick a fast enough card, but in most cases you should be able to pick a slower, larger card than a faster, smaller one. Large cards are critical if you want to record and hold a lot of footage.

SD Cards for TVs

Some modern TVs have integrated SD card slots, and nearly all modern TVs have USB ports. By slotting your card into an adapter, you can easily view the photos or video from a camera without needing to copy them to a PC first.

tv usb

This is dependent on the format you’re using, though. RAW images won’t display, for example, and you’ll need to check your TV’s manual for information on which video formats will play right off an SD card.

SD Cards for Mobile Devices

Many Android smartphones and most Windows Phones have a MicroSD card slot Your Next Phone Needs a MicroSD Card Slot -- Here's Why Some popular phones don't have microSD card slots -- but a lot still do, and you need one! Read More that you can use to augment the built-in storage capacity.

Here, you’ll get the best results from buying the largest, fastest card you can afford while staying compatible with your device. Between the two, capacity is more important than speed for a mobile device.

lg g4

This is even true of 4K video, which on a smartphone is often heavily compressed. The LG G4, for example, actually uses a bitrate of 30 Mbps for 4K shooting, which is below Class 4 card speeds.

Where you will notice a difference in speed is if you copy files to and from the card regularly (especially large video files) or the first time you drag your massive music collection onto the card. Given the low cost of Class 10 cards now, there’s little reason to choose anything slower.

SD Cards for Data Storage

Most laptops come with a built-in SD card slot these days. It’s primarily designed for getting photos off your camera or moving files from one device to another, but can also be used as an easy way to upgrade your storage.

Secondary Data Drives

If the card sits flush with the laptop’s casing, then you can leave it permanently inserted and basically use it as a secondary data drive.

laptop memory card

Unfortunately, on many laptops, the SD card actually protrudes from the slot by several millimeters, creating an untidy look and leaving it prone to being snagged. In these cases, there are a few possible solutions.

Some manufacturers, like the Transcend JetDrive Lite, have SD cards that perfectly fit into MacBook card slots. They may or may not also fit your Windows laptop, depending on the case design. Just be wary of inserting a card that’s too small in case it gets stuck and becomes impossible to remove.

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Along similar lines are HyperDrive adapters. Again, these are designed for MacBooks but may also fit Windows laptops. These MicroSD card adapters fit into regular SD card slots but are shorter than SD cards so do not stick out as far. You can find generic versions on Ebay, too, often called MiniDrive adapters.

Either way, if you’re using an SD card for storage, you want the fastest, largest card that will work in your laptop. Preferably 128 GB and U3 speed, with one exception in cases where you use the card to store something like your iTunes library, in which case speed will be less important once you have copied all the files over.

Data Backups

If you can find a card that fits your laptop’s SD slot perfectly, you can leave it inserted as a handy backup drive in conjunction with File History in Windows or Time Machine in OS X Schedule & Browse Time Machine Backups With These Powerful Tools From custom backup times to finding out where those 2 GB of new files are, the right apps can give you power and knowledge Apple's own tools just don't provide. Read More .

time machine

It’s a better option if you’re doing selective backups, since there are limits to the size of card you can get (e.g. there’s no way to clone a 2 TB drive to an SD card as of now) and the cards start to become less cost effective once you move beyond 128 GB.

Raspberry Pi

The Raspberry Pi needs an SD card Raspberry Pi: The Unofficial Tutorial Whether you're a current Pi owner who wants to learn more or a potential owner of this credit-card size device, this isn't a guide you want to miss. Read More (or MicroSD on a Pi2) to install the operating system, but the requirements are modest. You need a card of 4 GB or larger to use the NOOBS app which simplifies the installation and setup process How NOOBS For Raspberry Pi Can Help First Time Users There is something about the Raspberry Pi that might just put people off: until now, setting it up has not been particularly user friendly. NOOBS aims to change that! Read More , and the official recommendation is 8GB, Class 6.

pi card

You might want to use a larger card so you’ve got space for data storage as well, though you can use a USB flash drive for that if you need to.

Although most SD cards should work on the Pi, some users have experienced compatibility problems with certain card models. Before you settle on a card, it’s worth checking this list of working and non-working cards to see if yours has been tested.

SD Cards for Bootable Drives

A final good use for an SD card is as a bootable drive for your PC or laptop. You can set it up for emergencies if your computer fails to boot or if you want to test drive a new Linux distro Create a Bootable USB From an ISO With These 10 Tools Want to create a bootable USB drive from an ISO file? We've got the ten best bootable USB pendrive creators around. Read More .

Many laptops are not able to boot from the internal SD card slot, so you might need to use an adapter and plug it into a USB port. In this case, make sure your adapter is at least USB 3.0 USB Flash Drive Guide: 5 Things to Know When Buying One USB flash drives might seem mundane and straightforward, but there are a few tips and quirks that you should know before you buy your next one. Read More or it will be unusably slow.

sd cards

To create a Windows 10 boot disk How to Create an ISO Image of Your Windows System Need to backup and restore Windows without backup tools? It's time to learn how to make an ISO image of your Windows PC. Read More , you only need a card of at least 4 GB, but there’s no good reason to buy a card of this size any more. A 16 GB U1 card is well within most budgets and performs much better.

Which SD Cards Do You Have?

The falling prices of memory cards is making them easier to buy than ever. Unless you have specific requirements, you should never have to settle for a card that’s either too small or too slow.

That said, with a growing number of devices using SD cards, it’s always a good idea to check that you’re getting the right one for the job.

What memory cards do you use? Is there are brand you swear buy, and which ones do you always buy for a specific device? Share your thoughts and recommendations in the comments below.

Image Credits: Sandisk via nubobo, Fuji via Kristoffer Trolle, GoPro via Andreas Kambanis, LG G4 via Karlis Dambrans, Laptop Memory Card via Jeff Nelson, Pi Card via eliotpearson

Related topics: Buying Tips, Memory Card.

Affiliate Disclosure: By buying the products we recommend, you help keep the site alive. Read more.

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  1. Paul D Pruitt
    February 24, 2016 at 2:21 pm

    Fake Flash Test,, will rapidly test your card to see if it's fake. The website could use better production values but the program apparently works well. There is also a link to the slower H2TESTW, which was and may still be the last word in fake memory testers but can take hours to run.

  2. kammak743
    February 23, 2016 at 10:13 pm

    I have 5 memory cards. 2 sandisk ultra 8gb and 3 sandisk extreme 16gb. I always buy sandisk (my flash drives and ssd are all sandisk) because I have never had any reliability issues and they generally perform better than the quoted speed.