SD Card Speeds and What They Mean: UHS-1, V60, Class 10

Confusingly, there’s also the UHS bus type. For ultra-fast SD cards, these are probably more relevant. UHS-I cards have a theoretical maximum of 104 MB/s, while UHS-II cards top out at 312 MB/s. These aren’t necessarily their actual speeds, just what the connector is capable of. If you’re doing something heavy-duty, like recording 6K or 8K video, you’re probably going to be looking for a UHS-II card. These are usually indicated by the Roman numeral I or II.

Finally, there’s the Video Speed Class. These are denoted by a V symbol, followed by a number representing the minimum write speed, in MB/s. The speed classes are V6, V10, V30, V60, and V90. For example, a V6 means the card has a minimum write speed of 6 MB/s. Cards can obviously be faster than that, but if you need to hit a minimum speed, this is a good symbol to look out for.

It’s important to keep in mind that all of these symbols are just baselines. Most of the time, you can find actual speeds on a card’s listing page or its packaging, if not on the card itself. Be sure to check because sometimes the gap between minimum ratings and the card’s actual speed can be quite large.

Additionally, keep in mind that SD cards often have different speeds for reading and writing. If you need to take a dozen photos every second, it won’t matter if your card can read data really fast, it needs to write fast as well. Unfortunately, this can mean that despite the bevy of symbols and icons on your SD card, the best way to make sure it meets your needs is to just look up that card’s speeds directly.

Should I Get the Fastest Card?

Your natural instinct, after reading all this, might be to just buy the fastest SD card you can. But there is a bit of a trade-off. Faster SD cards generally cost more for the same amount of storage, so consider your use case carefully. If you need to transfer large amounts of data at once—either by storing lots of media to the card or reading huge amounts of data from the card—a faster card may help. However, if storage capacity is more important, a slower SD card may be more cost-effective.

For example, here’s a 128-gigabyte SD card designed for video work that can record up to 8K footage (depending on the format) and can read data at speeds up to 280 MB/s. It normally costs $150. But here’s another 128 gigabyte SD card that can “only” read data at up to 170 MB/s—it usually costs $45. You might end up paying a hefty premium for higher speeds, so it’s better to balance out what’s best for you.

You also need to consider what your device itself can do. For example, the Nintendo Switch is only capable of transfer speeds up to around 95 MB/s, so faster SD cards will be useless on it. Besides, you’ll get more use out of additional storage at that speed anyway. Speed is important, but it isn’t the only factor that matters.

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