SD Card Speed Classes Explained: U1, U3, V30, V90, A1, A2 and UHS-II
Memory cards are covered in small symbols. They are not marketing. Each one is a guaranteed minimum performance level, and choosing the right one decides whether your camera can record smoothly.
Speed class symbols
| Symbol | Minimum sustained write speed | Good for |
|---|---|---|
| Class 10 / U1 / V10 | 10MB/s | Full HD video, everyday photos |
| U3 / V30 | 30MB/s | 4K video, action cameras, drones |
| V60 | 60MB/s | High-bitrate 4K, fast burst photography |
| V90 | 90MB/s | 8K video and professional cinema cameras |
The headline "up to" speed on the front of the card is the maximum read speed. For recording video, the minimum write speed shown by the U or V class is what matters.
App performance: A1 and A2
A1 and A2 cards are tested for the small, random reads and writes that apps make. Choose A2 for Android phones and tablets if you run apps from the card, and for handheld consoles.
UHS-I vs UHS-II
UHS-II cards have a second row of contacts and can reach about 300MB/s. They are only faster in cameras and readers with UHS-II slots, but they work at UHS-I speed in everything else.
Which card should I buy?
- Phones, tablets, dash cams: Kingston Canvas Select Plus microSD 64GB or 128GB
- 4K action cameras and drones: SanDisk Extreme PRO microSDXC 128GB
- Everyday cameras: Kingston Canvas Select Plus SD 64GB or SanDisk Extreme PRO SD 128GB
- Professional UHS-II cameras, 4K/8K video: Kingston Canvas React Plus SD 128GB (V90, with UHS-II reader) or Lexar Professional 2000x SD 128GB (V90)
Read more in our microSD buying guide, or browse all memory cards.
Need help choosing? Call us on 01422 363983 (Mon–Fri, 9am–5pm) or email support@buykingston.co.uk.