Speed Class

What is Speed Class?

The speed class of an SD (Secure Digital) card refers to its minimum sustained write speed.

There are currently four main speed classes for SD cards: Class 2, Class 4, Class 6, and Class 10. Class 2 SD cards have a minimum sustained write speed of 2 MB/s, while Class 4 cards have a minimum sustained write speed of 4 MB/s. Class 6 SD cards have a minimum sustained write speed of 6 MB/s, and Class 10 cards have a minimum sustained write speed of 10 MB/s. In addition to these main speed classes, there are also two Ultra High Speed (UHS) speed classes: UHS Speed Class 1 (U1) and UHS Speed Class 3 (U3). UHS-I U1 cards have a minimum sustained write speed of 10 MB/s, while UHS-I U3 cards have a minimum sustained write speed of 30 MB/s. The speed class of an SD card is important to consider when using it for tasks that require fast write speeds, such as recording high-resolution video. Using a card with a lower speed class may result in dropped frames or other issues during recording.