Difference between SD, SDHC, and SDXC memory cards

Updated on February 20, 2018

Figuring out which memory card is best for you can be confusing. This is because memory cards come in different formats, sizes and speeds. To help you with making a good choice, here is a closer look at what SD, SDHC, and SDXC memory cards are.


An SD memory card

SD memory cards. The initials SD stand for Secure Digital. These were the first memory cards on the market and can only hold 2GB of data.

An SDHC memory card
An SDHC memory card

SDHC (Secure Digital High Capacity) memory cards replaced standard SD cards because of the need for more storage. These cards are capable of storing between 4GB to 32GB of data.

An SDXC memory card

SDXC (Secure Digital Extended Capacity) memory cards are the latest memory cards available. They have the largest memory storage capacity of between 64GB to 2TB.

Comparison Chart

SD memory cardsSDHC memory cardsSDXC memory cards
Storage capacity of up to 2GBStorage capacity of between 4 GB to 32GBStorage capacity of between 64GB to 2TB
Can only be used on compatible devicesBoth SDHC and SDXC are compatible with the other two types of cards


What is the difference between SD, SDHC, and SDXC memory cards? The main difference is the amount of data each can carry and the type of storage format.

Each of these memory cards represents a specific format used to store data. As mentioned earlier, the initials of the names of the memory cards stand for their formats. The main difference between these three categories of memory cards, however, is the storage capacity. An SD memory card can only hold up to 2GB of data; a SDHC memory card holds between 4GB to 32GB of data, while the SDXC can take up to 32GB.

SD memory cards were the first to be developed. Because of limitations in their capacity, the need to store more data led to the development of SDHC memory cards. Most devices meant to read SDHC and SDXC memory cards are reverse compatible, meaning that they can also read SD memory cards. SD memory cards, however, can only be used on compatible devices. These devices cannot use SDHC or SDXC memory cards.

In addition to format and size, memory cards come with a class rating these days. This is the speed with which information can be read and written by the memory cards. A slow read and write speed can affect the performance of a device, as it takes longer to write or read the data on the memory card. This data transfer rates are labeled 2, 4, 6, and 10. A class rating of 2 means that the card reads and writes information at speeds of 2MB/sec while a class rating of 10 means a speed of 10MB/sec.

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