Secure Digital Memory cards, also known as SD cards, as you may already know, are used extensively as a secondary storage device for portable devices like tablet computers, mobile phones, digital cameras and GPS navigation devices. And so with technologies like micro SD, micro SDHC, and micro SDXC, you might want to know what they mean and what can they do for you. While they all are secure digital memory cards, they have their differences, and knowing those differences may mean optimum performance for you and your portable devices.

Definitions

Getty Images/iStock/Vitalii Petrushenko

Micro SD

The SD card is the first generation of Secure Digital cards that was developed to improve our experience with the MMC (MultiMediaCard) standard. Since then, mini and micro SD cards have been developed to target mobile phones and improve their limited storage space.

MMC –  a memory card standard used for storage. Similar to the SD card but has a wide variety of storage capacity, more pins, lower speed in transfer rate, and is not as up to date as SD cards.

A micro SD memory card has a maximum space of 2 GB. It has a standard size of 11 mm by 15 mm. It has a maximum read and write speed of 25 MB/s, which is considered to be decently fast considering its small size. It is mostly used for mobile phones for storing photos, videos and simple applications. You can grab one at around $7.

Micro SDHC

Also known as Secure Digital High Capacity, it is much as the same as your micro SD cards, but has a higher storage capacity of 4 GB up to 32 GB. It is still a secure digital card that has the same standard size of 11mm by 15mm. It also has a higher transfer rate of potentially 50 MB/s and up to 150 MB/S.

But while SDHC cards are physically and electronically identical with your standard SD cards, older host devices for SD cards are not compatible with your SDHC cards, simply because SDHC cards are pre-formatted with the FAT32 file system while SD cards usually have a format of FAT12, FAT16 or FAT16B. However other host devices can accommodate the newer SDHC cards with a FAT32 file system or can undergo a firmware update. Meanwhile, micro SDHC host devices are required to accept older SD cards, meaning you can use your old SD cards with new technologies that can comply with an SDHC card.

Depending on the size of your micro SDHC card, prices can go from $6 up to $20.

Micro SDXC

Also known as Secure Digital eXtended Capacity, this micro SDXC card can support 32 GB up to a potential 2 TB GB of space. Like the other micro SD cards, it has a standard size of 11mm by 15mm. It has a high speed transfer rate of 50 MB/s and up to 312 MB/s.

While it does have the potential to reach 312 MB/s, it actually depends on the version of its design and its class speed. At version 3.0 with a UHS-1 (Ultra High Speed bus), it can go to up to 104 MB/s, and with a newer version 4.0 with a UHS-2 that was introduced in June 2011, it can reach up to 312 MB/s. Price varies at around $15 to $200.

Comparison Chart

Micro SD vs Micro SDHC vs Micro SDXC

What’s the difference between micro SD, micro SDHC and micro SDXC? Technically, there are a lot of differences but when talking about the key differences, there are just a few.

• With regard to storage capacity, micro SD has the least storage capacity at only around 2 GB. Micro SDHC comes second with up to 32 GB of storage space. Micro SDXC has the most storage capacity at a potential 2 TB, although, being a micro SDXC, storage capacity currently available is only 200 GB.
• Now for their speed: it depends mainly on their speed classes which are usually 2, 4, 6 and 10, with 2 having minimum serial data writing speed of 2 MB/s, 4 at 4 MB/s, 6 at 6 MB/s, and 10 at 10 MB/s. For micro SDHC and micro SDXC, usually their speed is marked by UHS 3 or a UHS 1. With UHS 1, minimum speed will be at 10 MB/s and UHS 3 at 30 MB/s.
• Regarding their compatibility, micro SD cards can comply with newer host devices. This would now mean that micro SD cards are compatible with SD, SDHC and SDXC host products. For micro SDHC cards, they are not compatible with SD host products but are compatible with SDXC and SDHC products. Lastly, micro SDXC cards are exclusively compatible with SDXC host products.

So to summarize, micro SDXC has a higher storage capacity than a micro SDHC and a micro SD card. For their speeds, micro SDHC and micro SDXC have a faster transfer rate than your micro SD cards. Prices on the other hand, will depend on their storage capacity and speed class.