Understanding Memory Cards: Class and Speed

When choosing a memory card for your smartphone, or just about any other high end electronic, one of the most important things that you can consider is actually one of the most overlooked features and that is how fast the card is. This guide will list and describe the differences that you can look for when choosing the fastest memory card for your cell phone and allow you to make the best informed decision when doing so.

Choosing a memory card with some Class

When measuring the speed of a memory card you are going to need to find out what Class it is. The higher the Class the faster the phone will be able to read and write information to and from that memory card.

Some devices won’t even work right if the memory cards Class isn’t high enough for that device. For example if you have a camcorder or a video recorder (especially a high definition video recorder) which is built to use a Class 6 memory card or higher and you try to use a Class 2 or a Class 4 SD card then your video recordings might error, might be fragmented, read “busy”, or might not work at all.

There are two forms of measurement that you can run across when buying a memory card and that is the cards “Speed Class” OR “UHS Speed Class”.

Speed Class vs. UHS Speed Class

Both “Speed Class” and “UHS Speed Class” measure the minimum sustained transfer speeds in flash memory and both systems of measurement are relatively easy to understand once you know what you are looking for.

Speed Class

As mentioned already Speed Class indicates how fast information and data can be constantly written to the memory card. The higher the Class the faster the speed in which your device can save information to the card.

Speed Class currently has four minimum constant write speeds available.

Class 2 – 2MB/s (16Mbps)

A Class 2 memory card is the slowest memory card available and can have data written to it at a minimum speed of 2 Megabytes (16 Megabits) per second.

Class 4 – 4MB/s (32Mbps)

A Class 4 memory card is the second slowest Class of memory card and can have data written to it at a minimum speed of 4 Megabytes (32 Megabits) per second.

Class 6 – 6MB/s (48Mbps)

Class 6 memory cards have a minimum write speed of 6 Megabytes (48 Megabits) per second.

Class 10 – 10MB/s (80Mbps)

Class 10 memory cards are the fastest memory cards available under the Speed Class rating system and have a minimum write speed of 10 Megabytes (80 Megabits) per second.

UHS Speed Class

UHS Speed Class memory cards are another type of memory card available on the market. UHS (Ultra High Speed) memory cards consist of the UHS Speed Class 1 (U1) and UHS Speed Class 3 (U3).

UHS Speed Class 1 (U1) - 10MB/s (80Mbps)

UHS Speed Class 1 has a minimal write speed of 10 Megabytes (80 Megabits) per second.

UHS Speed Class 3 (U3) - 30MB/s (240Mbps)

UHS Speed Class 3 memory cards have a minimum write speed of 30 Megabytes (240 Megabits) per second.

So what does all of this mean?

Most devices that require a higher class of card in order to function will be labeled as such. A video recorder for example may require a memory card with a speed class of UHS Speed Class 1 (U1) or a Class 10 card in order to record 4K video or even full HD video (1080p). If you tried to use a memory card with a lower speed class rating then it wouldn’t work.

If you don’t see a speed class requirement for your device you might want to still consider investing in a faster card in order to get the best performance possible. This could help to eliminate buffering or loading times when information is being written to the card.

Backwards compatibility

A memory card with a higher class rating should have no compatibility issues with devices requiring a lower class speed. So for example you could choose to use a UHS card in a non-UHS device or a Class 10 memory card in a device that requires a card with a minimum write speed of a Class 8 memory card.

The reverse however is not possible. You could not use a Class 6 memory card in a device that requires a Class 10 card even if you wanted to.

My recommendations

Future proofing

As far as memory cards are concerned investing in a card with a higher speed class rating is usually a good idea. Not only will this help to avoid incompatibility issues but it’s also a good way to future proof your memory card so that you can continue to use it as you upgrade your chosen devices. That way when you get the newest and greatest gadget or gizmo you can simply take your card out of the old one put it into the new one and be ready to go.

Where to buy your SD card

When buying a memory card I highly recommend that you buy it online from a store like Amazon. If you choose to buy it from a retail location you can find yourself paying 2 or 3 times more for the exact same card. Stick to shopping from reputable sites online when it comes to memory cards and you shouldn’t have any problem finding the best price on the best memory card for your device.

Other things to consider

While the speed class of a memory card is arguably one of the most important factors to consider when choosing a memory card there are a few other things that you should take into account as well. Its storage capacity (2GB, 4GB, 8GB, 16GB, 32GB, 64GB, etc.), what type of SD card it is (SD, SDHC, SDXC), its brand/quality (SanDisk, Samsung, Kingston, PNY, etc.) and even the length of its warranty (1 year, 3 years, 5 years, 10 years, Limited Lifetime, etc.).

Thank you for reading

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