SD Card Speed Classes: Which Class Do You Need?

SD card speed classes determine the minimum write speeds your card can sustain, directly impacting whether your camera, drone, or device can record without dropping frames or buffering. These letter-and-number ratings—like U3, V30, or A2—tell you exactly what each card can handle before you buy.

Picking the wrong speed class means missed shots, corrupted video files, or sluggish app performance. A Class 10 card works fine for casual photos but chokes on 4K video, while a V90 card is overkill for a basic point-and-shoot camera.

This guide breaks down each speed class rating, explains what the symbols mean, and helps you match the right card to your specific device and shooting needs.

Explore KingSpec's complete range of SD and microSD cards across all speed classes, from Class 10 to V30 and A2 ratings. Shop Memory Cards

Understanding SD Card Speed Class Ratings

SD card speed class ratings tell you the slowest write speed a card can maintain. This is what determines if your camera, drone, or other device can keep up with the data you’re throwing at it.

What SD Card Speed Classes Actually Mean

Speed class ratings represent the lowest write speed your SD card can hold during continuous recording. Your device needs a steady stream of data storage to avoid dropped frames or recording glitches.

The original Speed Class system uses a “C” symbol with a number inside. Class 2 means 2 MB/s, Class 4 is 4 MB/s, Class 6 is 6 MB/s, and Class 10 guarantees 10 MB/s minimum write speed.

These numbers are about sustained write speed—not just those quick bursts you see in marketing. A card might spike higher for a second, but the speed class tells you what it can actually keep up over time. That’s what keeps your video smooth and your photos saving without hiccups.

Speed Class vs UHS Speed Class vs Video Speed Class

There are a few speed class types because SD card tech keeps evolving. Each system fits different bus interfaces and recording needs.

UHS Speed Class uses a “U” symbol and works with UHS (Ultra High Speed) bus interfaces. UHS Speed Class 1 (U1) means 10 MB/s, and UHS Speed Class 3 (U3) means 30 MB/s. You’ll need UHS-I, UHS-II, or UHS-III cards for these ratings.

Video Speed Class uses a “V” symbol and is meant for modern video recording and newer memory tech. Here’s the breakdown:

• V6: 6 MB/s minimum
• V10: 10 MB/s minimum
• V30: 30 MB/s minimum
• V60: 60 MB/s minimum
• V90: 90 MB/s minimum

V60 and V90 only hit their rated speeds with UHS-II or UHS-III interfaces.

SD Express Speed Class includes E150, E300, E450, and E600, running from 150 MB/s to 600 MB/s for advanced stuff. You’ll only see these with SD Express bus interface cards.

Application Performance Class (A1 and A2) Explained

Application Performance Class rates random read and write speeds, which is a big deal if you run apps from your SD card on your phone or tablet. This isn’t the same as sequential write speed classes.

A1 cards must hit 1,500 read IOPS and 500 write IOPS, with at least 10 MB/s sustained sequential speed. A2 cards step it up to 4,000 read IOPS and 2,000 write IOPS.

The A rating shows up as a separate symbol and goes alongside other speed class ratings. You’ll notice A1 or A2 most if you’re actually running apps from the card, not just storing photos or videos.

How to Read SD Card Speed Ratings

Your SD card usually has a bunch of symbols and numbers. The speed class symbols are circles or shapes with numbers inside.

Here’s what to look for:

• C with a number: Original Speed Class (C10 is everywhere)
• U with a number: UHS Speed Class (U1 or U3)
• V with a number: Video Speed Class (V30, V60, V90)
• A with a number: Application Performance Class (A1 or A2)

Cards often show a mix of these. If you see U3, V30, and A2, that card promises 30 MB/s sustained write, works with UHS bus, and is solid for app performance.

Some cards also list max read speeds (like 100 MB/s or 170 MB/s), but that’s just peak transfer speed—not what matters for recording. The speed class symbols are what you care about for reliability.

Choosing the Right SD Card Speed Class

Different recording tasks need different minimum write speeds to avoid dropped frames or storage errors. Class 10 and U1 cards work for HD video and basic photos, while U3 and V30 are the go-to for standard 4K video. V60 and V90 are for pros shooting 8K or super high-bitrate footage.

Class 10 and U1: Basic Photography and HD Video

A Class 10 SD card guarantees at least 10MB/s write speed. U1 does too—they’re basically the same here. You’ll see both on a lot of cards.

These are perfect for:

• Full HD video recording at regular bitrates
• HD video at 720p or 1080p
• Everyday photography with DSLRs or mirrorless cameras
• Storing photos from compact cameras

Class 10 and U1 cards handle continuous JPEG shooting just fine. They’re also okay for RAW files if you’re not doing rapid bursts. For most daily shooting and Full HD video, these cards are reliable and affordable.

U3 and V30: 4K Video Recording Requirements

U3 and V30 both guarantee 30MB/s minimum write speed. Most 4K cameras need at least this to record smoothly.

4K video files are much bigger than HD. The higher resolution means more data gets dumped onto your card every second. U3 or V30 keeps up with that data stream.

These classes are best for:

• 4K video recording at regular framerates
• Burst shooting with RAW files
• Action cameras at high resolutions
• Drones shooting 4K

Check your camera’s manual for minimum speed requirements. Most consumer 4K cameras need U3 or V30. Some higher-end rigs shooting at bigger bitrates might need even faster cards.

V60 and V90: Professional 8K and High Bitrate Recording

V60 gives you a 60MB/s minimum, while V90 promises 90MB/s. These need UHS-II cards, which have two rows of pins instead of one.

Pro-level video work really needs these higher speeds. 8K video is a data monster. High bitrate 4K also needs more speed than standard 4K. V90 keeps your recording smooth and frame drops at bay for professional shoots.

When you need V60 or V90:

Your camera must support UHS-II to get these speeds. If you use a V90 card in a UHS-I camera, you’re stuck at UHS-I speeds. Always check your camera specs before dropping money on the fastest cards.

A1 vs A2: Speed Classes for Smartphones and Apps

A1 and A2 measure random read/write performance, which is what matters for running apps and games—not so much for video.

A1 cards offer at least 1500 IOPS random read and 500 IOPS random write. A2 cards jump to 4000 IOPS read and 2000 IOPS write. IOPS is just input/output operations per second.

Phones and tablets benefit from A1 or A2 because apps constantly read and write little bits of data. Games and apps launch faster. Your phone just feels more responsive. A2 is pricier, but if you care about app speed or mobile gaming, you’ll notice the difference.

Upgrade your smartphone, camera, or drone with KingSpec's 128GB microSD cards featuring fast UHS speeds and A1/A2 performance. Browse 128GB MicroSD Cards

SD Card Speed Class Performance and Applications

Speed class ratings make a real difference in how well your SD card handles tasks like burst photo shooting, high-res video, or gaming. Devices need certain write speeds to work right, and picking the right class saves you from buffer overflows, dropped frames, and lag.

Does Speed Class Affect Photo Burst Mode?

Absolutely—speed class matters for burst mode. When you fire off a burst of photos, your camera’s dumping a pile of images to the SD card every second. If your card can’t keep up, the camera’s buffer fills and you’re forced to wait.

Pro cameras shooting RAW need faster cards than ones shooting JPEG. A high-res RAW photo can be 25-50MB per shot. If you’re shooting 10 frames per second, that’s 250-500MB/s needed just to keep up. That’s intense, right?

For most burst shooting, U3 or V30 cards work well with today’s cameras. They give you 30MB/s minimum, enough for JPEGs and moderate RAW bursts. If you’re a pro with huge files and a high-end camera, you’ll want UHS-II SD cards rated V60 or V90 for 60-90MB/s. If you want to check out some solid options, Kingspec Tech has a variety of memory cards for different needs.

Drone and Action Camera Speed Requirements

Drones and action cams recording 4K video need at least 30MB/s write speeds. Most brands list U3 or V30 as the minimum. 4K at 60fps bumps the data rate even higher, so you really do need these ratings to avoid dropped frames.

Action cameras often record high-res, high-bitrate video. A 4K video at 100Mbps needs about 12.5MB/s, but you’ll want some headroom to avoid glitches. Cards below Class 10 or U1 just won’t cut it.

For 5.3K or higher, aim for V60 cards—they do 60MB/s minimum. And don’t forget about capacity: 4K video eats up around 375MB per minute, so a 64GB card gives you about 2.8 hours. If you don’t want to swap cards mid-shoot, go for 128GB or 256GB.

Gaming Consoles and SD Card Speed Needs

Gaming consoles like the Nintendo Switch need SD cards with certain speed ratings for smooth gameplay. The Switch accepts standard SD, SDHC, and SDXC cards, but you'll get the best results with UHS-I cards that hit transfer speeds around 60-95MB/s.

Game file sizes? All over the place. Some indie games barely hit 2GB, but big titles can balloon past 10 or even 15GB. With a 128GB card, you’re probably fitting 8-12 large games or maybe 20-30 smaller ones. Faster cards do help with loading times, though honestly, most folks won’t notice much difference between U1 and U3 cards for regular gaming.

Steam Deck and other portable gaming systems run better with speedy cards. They’ll work with Class 10 cards, but U3-rated microSD cards shave down those annoying game load times. A 256GB or 512GB microSD card gives you room for plenty of games, so you won’t have to delete stuff every week. If you see Class 2, 4, or 6 cards, just skip them—those old speed classes drag down performance in a way that’s hard to ignore.

KingSpec SD Cards: Speed Classes for Every Use Case

KingSpec has SD and microSD cards in a bunch of speed classes, so you can match the card to what you actually need. Their V30-rated cards are solid for 4K video recording in cameras, drones, or action cams, with 30MB/s sustained write speeds. Capacities range from 64GB up to 1TB.

If you’re just looking to expand storage on a tablet or phone, KingSpec’s U1 cards do the job without costing too much. They’re great for photos, music, and regular video files. The 32GB and 64GB sizes cover basic needs if you’re not chasing top speeds.

Anyone shooting 8K video or doing high-speed photography should check out KingSpec’s UHS-II cards when they’re available. These cards keep up with pro cameras and high-bitrate video. KingSpec uses NAND flash memory and builds in protections against water, temperature swings, and X-rays. If you buy from a trusted seller, you’ll get legit products and the manufacturer’s warranty.

Conclusion: SD Card Speed Classes

Choosing the right SD card speed class ensures your device captures every moment without buffer delays or dropped frames. Match Class 10 or U1 to basic photography, U3 or V30 to 4K video, and V60 or V90 to professional high-bitrate recording for reliable performance.

Before buying, check your device's speed class requirements in the manual or specifications. Using a card that exceeds minimum requirements future-proofs your setup and prevents recording failures during critical shoots.

Need help selecting the perfect microSD card for your specific device? Discover our recommendations: Best Micro SD Card: Complete Buying Guide 2026

Frequently Asked Questions: SD Card Speed Classes

Speed class ratings can get confusing with all those symbols and numbers. Here are some questions that come up a lot about speed classes, card types, and what those ratings actually mean.

What is SD card speed class?

SD card speed class indicates the minimum sustained write speed your card guarantees. The SD Association created these ratings to help match cards to devices. There are four main systems: Speed Class (C2-C10), UHS Speed Class (U1-U3), Video Speed Class (V6-V90), and SD Express Speed Class (E).

Is V30 faster than class 10?

Yes, V30 is three times faster with a minimum write speed of 30MB/s versus Class 10's 10MB/s. Cards often display both ratings—if you see C10 and V30, the card meets the higher V30 standard. V30 handles 4K video recording without dropping frames, while Class 10 works for Full HD.

What are the 4 types of SD cards?

The four types—SD, SDHC, SDXC, and SDUC—indicate storage capacity, not speed. SD maxes at 2GB, SDHC covers 4GB-32GB, SDXC spans 64GB-2TB, and SDUC ranges from 4TB-128TB. MicroSD cards follow the same naming system with identical capacity ranges.

Is A1 or A2 microSD faster?

A2 cards are faster for app performance with 4000 IOPS random reads and 2000 IOPS random writes versus A1's 1500/500 IOPS. Android devices benefit most—apps open quicker and run smoother when installed on A2 cards. Some A2 cards require USB 3.1 Gen 2 interfaces to reach full speed.