If you're using a microSD card in something like a GoPro or other small camera or camcorder that records high-resolution 4K video, speed matters. And just like with their bigger siblings, SD and Compact Flash cards, the speed of microSD cards vary widely from card to card.
The even-numbered class designations for SD and microSD cards, like Class 6 or Class 10, were supposed to provide an easy way to see if a card was fast enough for a particular use. And they did . . . for a while. But the capabilities of the newest cameras need something better than just Class 10. Most Class 10 cards won't work well in 4K video cameras like the GoPro HERO6 Black or GoPro HERO5 Session, for instance.
So you really need to look further to the read and write speeds. Of these, the write speed is by far the most important for most camera uses. That tells you how fast you can get data on to the card. That doesn't tend to matter as much when using microSD cards in smartphones or GPS units, but it does matter for cameras when you're shooting in burst mode or recording high definition 4K video or super fast framerates. The read speed, which is often used in marketing, tells you how fast you can get data off the card. With the speed tests and rankings below, I'm focusing on the write speeds and basing them on my own independent real-world testing.
But manufacturers don't always make it easy to see what the read and write speeds are. Names like "Ultimate," "Extreme," and "Elite Performance" aren't particularly helpful, especially when speeds are improving so rapidly and manufacturers are recycling the same card names with newer cards with different specs. And some manufacturers advertise speeds measured in megabytes per second, while others use more cryptic multipliers like 633x, making it hard to compare.
So I've been putting some of the microSD cards that are most readily available to the test. My focus here is on their speed for recording video and burst mode photos in the current generations of action cams like the GoPro HERO5 Black.
Current Top 3
Here are the ones that fill the top 5 spots in my tests of sequential write speed, the measure that's important for shooting high-resolution video. These are all more than fast enough for 4K video. As you can see in the detailed table below, some models, like the SanDisk Extreme Pro line, have several models that rank amongst the fastest in my tests because the manufacturers reuse the name as they come out with newer, faster cards.
1. SanDisk Extreme PRO V30A1 rating for app speed. It's rated for 90 MB/s sequential write speed and 100 MB/s, and in my tests, it came very close to both.
Find them at: Amazon
2. SanDisk Extreme PLUS U3
3. Samsung Pro+ (Samsung Pro Plus) U3
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Real-World Speed Test Results
Below is the full list of my microSD speed test results. These are sorted by default by descending sequential write speed--the value that's most relevant to using the cards in high-resolution cameras--but you can click on the column headers to sort by other criteria or use the search bar to filter by brand or model number. You can also scroll the table right to get the other columns.
|Brand||Model #||Speed Class||UHS||Tested Write / Seq||Tested Read / Seq||Tested Read / But||Tested Write / Ran||Rated Read MB/s||Rated Write MB/s|
|SanDisk||Extreme Pro (SDSQXCG)||V30||UHS-I||88.3||93.9||90.6||72.7||100||90|
|SanDisk||Extreme Plus (SDSQXSG)||U3||UHS-I||87.8||86.0||83||80.8||95||90|
|SanDisk||Extreme Pro (SDSDQXP)||U3||UHS-I||87.6||85.2||82.4||80.3||95||90|
|SanDisk||Extreme PLUS (SDSQXBG)||U3||UHS-I||87.4||91.5||90.8||86.4||100||90|
|SanDisk||Extreme PLUS (SDSQXWG)||V30||UHS-I||87.2||91.0||90.3||85.3||95||90|
|Samsung||Pro Select (MB-MF)||U3||UHS-I||85.0||91.7||90.6||84.6||100||90|
|Samsung||EVO Select (MB-ME)||U3||UHS-I||84.4||86.8||82.9||77.0||100||90|
|Samsung||Pro Select (MB-MF)||U3||UHS-I||84.3||93.2||88.6||80.9||100||90|
|Transcend||Ultimate 633x (TS32GUSDU3)||U3||UHS-I||73.7||91.1||87.7||18.2||95||85|
|Samsung||EVO Plus (MB-MC||U3||UHS-I||70.8||91.7||90.6||64.7||100||60|
|Samsung||EVO Select (MB-ME)||U3||UHS-I||70.3||91.0||88.1||65.2||100||60|
|SanDisk||Extreme PRO (SDSQXPJ)||U3||UHS-II||68.9||211.5||205.3||13.0||275||100|
|PNY||PRO Elite (P-SDU32GU395PRO-GE)||U3||UHS-I||55.3||88.1||81.6||3.7||95||90|
|SanDisk||Ultra Plus (SDSQUSC)||C10||UHS-I||50.3||92.2||88.7||12.9||80||-|
Obviously, this doesn't include every microSD card available. It's a growing list that I try to update regularly as new cards are released and become readily available. I buy all of these cards myself--there are no sponsored tests or freebies. If you have one you think should be added to the list, let me know in the comments.
Real-World Speed Tests
In real-world use, a range of technical factors in the camera and its transfer hardware and software can prevent you from hitting the speed numbers on the card's packaging. What I'm focusing on here is real-world uses, not scientific lab results that can't be replicated in practical use.
In conducting these tests, my objective is to test the performance that we can realistically expect using off-the-shelf hardware in normal use.
There are two things I am not trying to do. I'm not trying to replicate the manufacturers' benchmark lab tests. And I'm not trying to play gotcha and test whether the speed ratings the manufacturers claim are accurate. There are, after all, several things that can affect the speeds you can get out of cards in practice.
What I am trying to do is find out which cards perform best in real-world conditions and how they compare relative to each other. Because those are the things that matter to me when I'm trying to decide which card to buy. In short, I'm looking for practical speeds, not theoretical speeds.
So I'm using a real-world computer setup, not some high-end custom rig optimized to squeeze every last bit of bus transfer speed but not much good for actually processing photos and videos. There are dedicated hardware devices that exist only to test the speed of memory cards. Those are ridiculously expensive and not useful for any other purpose. Instead, I'm using readily available standard hardware that photographers might have on hand.
For the reader, I'm using a Lexar LRWM05U-7000 USB thumb reader. It's one of the two options that comes with the Lexar 1800x microSD cards. I've found it to be the fastest of the readers that are readily available—faster even than my Lexar Professional Workflow microSD reader—and because it connects directly to the computer's USB port, it eliminates any potential issues with cables or external card reader interfaces. It's connected via USB 3.0 and is UHS-II compatible.
For the software, I'm using the benchmarking suite in Digital Media Doctor by LC-Technology. All cards were new or near-new and freshly formatted. Because it's quite normal for results to vary a bit between tests, I'm running each set of tests three times and averaging the results.
For the computer, I'm using an iMac Retina 5K late-2014 with an internal SSD. There are faster, more powerful computers that might squeeze out higher transfer rates, but this provides a useful real-world platform that is widely used and available.
And, finally, the cards themselves. I buy all of these myself through standard retail. I don't accept freebie cards or conduct sponsored tests.
The Notes / Definitions
All speed ratings I'm using here are in MB/s (megabytes per second), which is not to be confused with Mb/s (megabits per second). Megabits per second is the measure more commonly used by cameras and in recording video. There are 8 bits in a byte, so to get from megabits per second to megabytes per second you multiply by 8. So 80MB/s is the same as 640Mb/s. Here's a handy conversion calculator.
X Rating vs MB/s. Some manufacturers use a more cryptic x rating in place of MB/s. Lexar, in particular, has long used this system. It comes from the old way of measuring the speed of CD-ROM drives when the standard speed of a CD-ROM drive was 150KB/s. Each x, therefore, equals 150KB/s.
Here's a quick cheat sheet for converting some of the common x ratings to MB/s:
SDHC vs SDXC
The codes microSDHC and microSDXC are useful in determining what size card will work in your device. If your device specs say that it only works with microSDHC, then you'll want a card that's 32GB or smaller.
SDHC (Secure Digital High Capacity) is a design specification that refers to SD cards that are between 4GB and 32GB in capacity and formatted with the FAT32 filesystem. FAT32 supports individual files up to a maximum of 4GB.
SDXC (Secure Digital eXtended Capacity) refers to SD cards with a capacity larger than 32GB and with a maximum theoretical limit of 2TB. They're formatted in the exFAT filesystem.
Just like SD card, microSD cards are given a speed class rating that refers to its category for writing data, with each category describing a real-world video recording use. These apply the same to microSDHC and microSDXC cards.
V90. The V-class is a new designation created to designate cards that are designed to work with the speeds required for 4K video and faster. The SD Association added some lower numbers to make them backward compatible with the older class designations (e.g. Class 10 and Class 6), but the most important ones are V30 and above.
Memory cards in the V90 class are rated to support a minimum sequential write speed of 90MB/sec. Their primary market is for cameras that shoot 8K video, and for now, those are pretty rare, but the class provides room to grow.
V60 is applied to cards that support a minimum sequential write speed of 60MB/sec. They're aimed primarily at cameras that record 4K video.
V30 is applied to cards that support a minimum sequential write speed of 30MB/sec. These are designed to support at least full HD video and some 4K video cameras that record 4K at lower bitrates.
U3 is designed to support 4K video recording at a sustained video capture rate of 30MB/s. This class overlaps with the newer V30 class.
U1 is designed to support real-time broadcasts and HD video (720p and 1080p) with a minimum serial write speed of 10 MB/sec. This overlaps with the newer V10 class.
Class 10 is designed to support 1080p recording at a minimum (but again, not at all framerates) with a minimum serial write speed of 10 MB/sec.
Classes 2, 4, and 6. Class 2 supports standard definition video recording with a minimum serial write speed of 2 MB/sec. Classes 4 and 6 are designed to support from 720p and 1080p video (but not all framerates) with a minimum serial write speed of 4 MB/s and 6 MB/s respectively. Most newer cameras need cards faster than these, so memory cards in these speed classes aren't as commonly available now.
What is the A Rating (e.g. A1)?
The A1 rating is a new type of speed specification that's relevant for running apps from the memory card. The A rating is a separate specification, not one in the same sequence. So it’s possible for a card to have both A1 and V30 ratings, for example.
Up to this point, the primary market for memory cards has been for storing media like videos or photos. But increasingly, devices are able to run apps directly from a memory card. And that requires a different type of interaction with the space on the memory card--specifically, random read and write speeds and small chunks of data are placed wherever on the card there's space for them.
So the new A specification (for App Performance) incorporates the random read/write speed. If you're buying a memory card for a camera, it's not especially relevant because what's requires on those is sequential speed. So if you’re recording video (or shooting photos), the speed classes you want to look for are the ones starting with V (e.g. V30 or V60) or U (U1 or U3). But if you're buying a memory card for a gaming device or smartphone or some other kind of device that runs apps and uses SD or microSD memory cards, the A1 rating is designed as a guide for what cards are best suited to that kind of use.
UHS-I vs. UHS-II
Newer microSDHC and microSDXC cards have a feature called ultra high-speed bus, which refers to the interface. So far, there is UHS-I and UHS-II.
UHS-II is the newer, and potentially faster, system but adoption is still not widespread. And a UHS-II isn't necessarily guaranteed to be faster than every UHS-I card in practice, as you can see from the test results above. The UHS-I category refers a type of interface that has a potential maximum speed of 104MB/sec.
The product labeling for cards with this technology will have either UHS-I or UHS-II, or sometimes just I or II. Technically, it should be Roman numerals, but you'll sometimes see it listed with a number 1, like UHS-1, even by some manufacturers.
You can also tell them apart by looking at the cards themselves. UHS-I cards have a single row of pins on the back.
But it's important to note that taking advantage of the potential speed increases of UHS-II requires that both the card and the host (e.g. card reader or camera) support it. Using a UHS-II card in a camera or host that only supports UHS-I will result in it falling back to UHS-I speeds. Put another way, if you use a UHS-II card in a card reader or device that's only rated for UHS-I, you'll only get a maximum potential of UHS-I.
- There are counterfeit memory cards out there. Buying from a reputable retailer helps minimize the risk of getting a fake.
- Memory cards are complicated electronic products. A small percentage of electronic products end up being faulty from the manufacturing process. So it's good practice to test your card before using it in a mission-critical application. Better yet, have spare/s as backup.
- Memory cards are not designed for long-term archival storage of photos and video. It's good practice to download the data as soon as practical and get it backed up securely.
- Format the card in the camera rather than with your computer. It reduces the risk of formatting problems.
Images and product information from Amazon Product Advertising API were last updated on 2018-05-27 at 00:54.