SD card speed classes explained: V30, V60, and V90
Learn what V30, V60, and V90 guarantee, how UHS-I and UHS-II differ, and how to match an SD card to a camera's actual recording requirements.
1. Video Speed Class is about sustained writing
Cameras must keep writing while they record. A card that reaches a high peak speed but cannot sustain the required rate may stop recording or drop frames. Video Speed Class was designed to communicate an assured minimum sequential write rate under defined conditions.
V6, V10, V30, V60, and V90 correspond to 6, 10, 30, 60, and 90 MB/s. The class is a floor, not the card's advertised maximum read speed.
2. Match the camera's requirement, not the resolution label
Two cameras recording 4K can have very different bitrates, codecs, frame rates, and data patterns. One may work with V30 while another mode requires V60 or V90. The camera manual and the manufacturer's approved-media list are stronger evidence than a generic claim that a card is suitable for 4K or 8K.
Convert bitrate to a rough byte rate by dividing megabits per second by eight, but do not treat that result as the only requirement. Cameras may use bursts, overhead, multiple streams, or conservative qualification rules.
3. UHS-I and UHS-II describe the bus
UHS-I cards have one row of contacts. UHS-II cards add a second row and can support a faster bus when the camera and reader also support it. V60 and V90 are associated with UHS-II or faster bus modes in the SD standard.
A UHS-II card can often operate in a UHS-I device, but only at the supported fallback speed. Paying for V90 may still help when moving files through a UHS-II reader, but it will not turn a UHS-I camera slot into UHS-II.
4. Read speed and write speed solve different problems
Write performance matters while the camera records and while its buffer clears after a burst. Read performance matters when ingesting files. Packaging often gives the largest number to read speed, so confirm which direction each number describes.
For still photography, buffer-clear tests in the exact camera can be more revealing than a label alone. For video, the required sustained class is the first filter.
5. Capacity and authenticity matter too
SDHC covers more than 2GB through 32GB, while SDXC covers more than 32GB through 2TB. Confirm that the camera supports the capacity and file system. Larger cards reduce swaps, while several smaller cards can limit how much work is exposed to one failure or loss.
Counterfeit cards can report false capacity or speed. Buy from an established seller, test new cards before an important job, format them in the camera, and keep a sensible rotation.
Frequently asked questions
Does V90 mean 90 MB/s maximum speed?
No. It indicates an assured minimum sequential write rate of 90 MB/s under the Video Speed Class standard's conditions. Maximum read and write figures are separate.
Will a V90 card improve every camera?
No. The camera must support the relevant bus and benefit from the faster card. Follow its manual or approved-media list.
Is U3 the same as V30?
Both indicate a 30 MB/s minimum in their respective protocols, but they use different access methods. Match the class your host device specifies.
Primary references
Technical standards can change. We use the relevant standards organizations as primary references and recommend checking the device maker's current manual.