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SD Card Overview: SD, SDHC and SDXC – What’s the Difference?

Many people get confused when it comes to understanding the many different kinds of SD cards. If you’re one of those people then we’ll clear up all misconceptions for you.



SD Card Overview

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SD cards are about as commonly used as they are commonly misunderstood. We all use them in a variety of devices, whether it’s computers, digital cameras, smartphones, or gaming systems. Everyone loves how portable they are and how easily they can be used to transfer tons of data. But many people get confused when it comes to understanding the many different kinds of SD cards, especially when it comes to SDHC vs SDXC. If you’re one of those people then we’ll clear up all misconceptions for you.

Full SDMicro SDSD Card Capacity
SDSD CardSD Micro Card2GB and less
SDHCSDHCMicro SDHCmore than 2GB, up to 32GB
SDXCSDXCMicro SDXCmore than 32GB, up to 2TB

The SD Card

The “SD” in SD card stands for Secure Digital. All SD cards, whether they be micro, SDHC or SDXC, are memory cards that use virtual flash memory. They are different from conventional hard drive disks because they don’t use moving mechanical parts. Instead, all the data is recorded “virtually” on the inner circuitry. It is this technology that allows all SD cards to be so small yet still contain as much as over 500gb in some cases.


Here’s where people tend to get confused, but it’s actually quite simple. SDHC stands for Secure Digital High Capacity and SDXC stands for Secure Digital eXtended Capacity. These two cards, contrary to popular belief, are not necessarily faster than standard SD cards but instead have higher data capacities. SD cards have a maximum of 2gb. SDHC has a maximum of 32gb, and SDXC has a maximum of two terabytes.


There is, in fact, a fourth data size class of SD cards called SDUC, which stands for Secure Digital Ultra Capacity. They can hold up to 128 terabytes of data. These are rare and expensive cards that are not sold at normal vendors, often not even online ones. These cards are normally purchased by people working in professional HD film editing that need to have thousands upon thousands of gigabytes of high quality visuals and audio all in one place.

Micro SD Cards

Micro SD cards are pretty self-explanatory. The size classes of SD cards, including SDHC and SDXC, have their own micro variants. They are no different than regular SD cards, including data capacity and speed, except that they are physically smaller in size. Micro SD cards exist for devices that are too small to have a regular sized SD card port installed. Many modern day music players or cellphones have micro SD card slots now, although laptops and most desktop PCs tend to have regular SD card slots still.

Speed Classes

If you’ve ever heard anyone arguing the merits of SDHC vs SDXC based on speed instead of size, then now you know they were mistaken. Contrary to popular belief, transfer and upload speed is not dependent upon whether a card is SDHC or SDXC. Speed classes are designated with a number. There are four standard speed classes: 2, 4, 6 and 10. 2 is the slowest and 10 is the fastest. Any size class can have any kind of speed. There are Class 4 SDHC cards and Class 6 SDXC cards for example. There are also two UHS, or Ultra High Speed classes, called 1 and 3. These are even faster than 10 but are more expensive and harder to find.

SDHC vs SDXC: Which Should I Buy?

By now you’ve probably realized that regular SD cards are too low in capacity and SDUC cards are too expensive. So the issue people often face when purchasing a new memory card is that of SDHC vs SDXC. Which of these is the better buy?

This really depends on what your needs are. As mentioned earlier, the only thing that differentiates the two is maximum data capacity. If you need only 30gb for your smartphone for photos and songs, an SDHC will do fine. If you need more than 30 on a single card then you have to go with an SDXC.

In most cases when it comes to SDHC vs SDXC, the latter is better. 32gb is not that much these days. Anyone looking to back up all their computer data is going to need hundreds of gigabytes at least, something an SDHC won’t be able to do. Plus video games and movies are only getting bigger and bigger. At this rate SDHC cards will become outdated in a few years.

SDHC vs SDXC is still one of the most commonly talked about topics when it comes to SD cards, and while SDHC cards still have their uses for the price, SDXC is superior in most circumstances. It’s probably better to buy an eXtended Capacity card now and have it be useful for several years instead of having to just inevitably upgrade sometime down the line.

Hopefully this has cleared up all the facts surrounding Secure Digital cards and given you a sense of what people are looking for when they ask about SDHC vs SDXC.