Guide to Speed Classes for SD and microSD Cards
When choosing an SD or microSD card for your device—whether it's a smartphone, camera, drone, or gaming console—it's essential to understand the various speed classes available. The speed class of a card determines how quickly data can be read from or written to it, which can significantly affect performance, especially for tasks like 4K video recording or burst photography.
Below is a breakdown of the most commonly used SD/microSD speed classes and what they mean for your usage.
What Is a Speed Class?
A speed class is a standardized way to represent the minimum sustained write speed of a memory card. It’s typically measured in megabytes per second (MB/s). There are several systems of speed classifications:
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Speed Class (C)
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UHS Speed Class (U)
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Video Speed Class (V)
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Application Performance Class (A)
Each class is designed for different types of devices and usage needs.
SD and microSD Card Speed Class Chart
| Class Type | Class Label | Minimum Write Speed | Best For |
|---|---|---|---|
| Speed Class | C2 | 2 MB/s | Standard definition video |
| C4 | 4 MB/s | HD video, photos | |
| C6 | 6 MB/s | HD video | |
| C10 | 10 MB/s | Full HD video | |
| UHS Speed Class | U1 | 10 MB/s | Full HD video, action cams |
| U3 | 30 MB/s | 4K video, burst photography | |
| Video Speed Class | V6 | 6 MB/s | Basic HD video |
| V10 | 10 MB/s | Full HD video | |
| V30 | 30 MB/s | 4K video | |
| V60 | 60 MB/s | 8K video, professional video | |
| V90 | 90 MB/s | High bitrate 8K, high-frame-rate video | |
| Application Class | A1 | 10 MB/s + 1500 IOPS read | Apps on smartphones/tablets |
| A2 | 10 MB/s + 4000 IOPS read | Faster app performance, gaming, multitasking |
How to Choose the Right Speed Class
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Basic Storage (Documents, Light Photos): C4 or C6
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Full HD Video / DSLR Photography: C10, U1, V10
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4K Video / Drones / GoPro: U3, V30
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8K or RAW Video / Professional Cameras: V60 or V90
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Smartphones & Tablets (App Performance): A1 or A2
Real-World Considerations
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Read vs. Write Speed: Manufacturers often advertise maximum read speed, which is not the same as the sustained write speed guaranteed by the speed class.
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Fake Cards: Buy from reputable retailers. Counterfeit cards may misreport their speed and storage.
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Device Compatibility: Always check your device’s manual or specs to ensure it supports higher-speed classes like UHS-II or V60+.
Choosing the right speed class ensures your SD or microSD card can handle the demands of your device. Whether you're recording ultra-high-resolution videos or running apps from the card, understanding these classes will help you avoid slowdowns, errors, or corrupted files.