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TOP > SD/SDHC/SDXC Memory Card Lineup > What Is "SD Speed Class"?
The SD Association has defined a hierarchy of classes as a guideline for speed performance. It is easy to select a card based on its transfer speed because speed classes are indicated both on compatible devices and cards.
There are four SD Speed Classes, Class 2, Class 4, Class 6, and Class 10.
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Transfer speed is a minimum of 2MB/sec. |
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Transfer speed is a minimum of 4MB/sec. |
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Transfer speed is a minimum of 6MB/sec. |
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Transfer speed is a minimum of 10MB/sec. |
For example, when reading/writing with a Class 2 card, the transfer speed is over 2MB/sec. Class 4 is over 4MB/sec, Class 6 is over 6MB/sec, Class 10 is over 10MB/sec. The transfer speed when reading/writing depends on the compatible device and card, and they belong to their own respective classes, and the class that the device or card belongs to is indicated by a mark on the product or the package.
A speed class for the standardized UHS interface, which is even faster, has been defined.
It is a guideline for UHS interfaces.
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Reading and writing speeds are a minimum of 10 MB/sec with devices that support UHS interfaces. |
The transfer speed is based on the result as measured under conditions regulated by the SD Association.
*Read and write speeds may vary depending on the read and write conditions, such as devices you use and file sizes you read and/or write. (For purposes of measuring write speed in this context, 1 MB = 1,000,000 bytes).
