Welcome to the ultimate guide to memory cards! It is very likely that at the time of buy an SD or micro SD card You would think that all memory cards were the same, but you have almost certainly seen that there are many types of cards with a lot of different features.

Depending on the device you need the SD card for, you need to choose the appropriate UHS BUS class, Speed ​​Class, Application Performance Class, etc…

V30? SDXC or SDHC? How much capacity do I need? These are questions that many people ask themselves on a daily basis. To resolve all these doubts, I have prepared for you this SD and micro SD memory card buying guide.

And if you get to the end of the article, I leave you the best deals on sd and micro sd cards updated!


    What is an SD card?

    An SD card (short for SecureDigital) is a memory card designed to store data and content on portable devices, such as mobile phones, digital photography and video cameras, tablets, game consoles or GPS navigators, among others.

    Today, SD cards are undoubtedly one of the most popular storage media, thanks in part to the large capacity they offer in such a small size.


    Before buying an SD card, you should take into account, broadly speaking, three factors:

    • type or size
    • Ability
    • Read and write speed

    SD card types

    There are mainly 3 types of SD card according to their size:

    1. SD (or full format SD)
    2. Mini SD
    3. Micro SD

    For a few years now only SD and micro SD remain on the market. The mini SD is obsolete and was totally obsolete.

    • SD: It was the first model to appear on the market. It has dimensions of 32 mm high x 24 mm wide x 21 mm thick. It is currently the most common format among DSLR digital still cameras and some camcorders.
    • Mini SD: They are the first evolution of SD cards and are 21.5mm high x 20mm wide x 14mm thick. They are currently deprecated.
    • Micro SD: micro SD is the most common format in small devices. They can be found on mobile phones, tablets or game consoles. The size of the micro SD is 15mm high x 11mm wide x 10mm thick.

    What is a micro SD card?

    Micro SD is a variant of flash memory of the Secure Digital type. With permission of Huawei NM Cards, micro SD are the smallest memory cards. They have a size of only 15x11x10 mm.


    Undoubtedly, the great advantage of this type of memory card is its small size. MicroSDs allow you to store a large amount of information in a very small space. Another point in its favor is the current price of these cards, which makes the price/capacity ratio very high.

    Image: SD Association

    Which devices use SD or micro SD memory cards?

    Despite their long history, SD cards are still the current standard chosen to expand the memory of many devices, such as:

    • 📱 smartphones
    • 📹 GoPro-like action cameras
    • 📷 cameras or DSLR
    • 🎮 Nintendo Switch type game consoles
    • 📟 tablets
    • etc

    That the manufacturers have decided on a card format makes it much easier. Not too many years ago, choosing a memory card was a bit chaotic as we had a hodgepodge of different types such as memory sticks from Sony, the xd of Olympus, or the compact-flash (which are still in use today in the professional field).

    Although not all manufacturers currently opt for SD or Micro SD, for example Huawei uses the NMCard in your high-end phones and some professional camcorders from Sony have memory card slots XQD.


    How to choose the best micro SD memory card?

    In order not to complicate ourselves too much, these are the 4 basic points that you must take into account before buying a memory card:

    1. card type
    2. Class
    3. The bus
    4. The capacity
    5. The brand

    How many types of micro SD cards are there?

    Yes, many people think that all micro SD memory cards are the same, and even though they actually look the same, there are many differences between them. One of the objectives of this micro sd buying guide is that you learn to differentiate them and buy the most suitable micro SD to your device.


    Let's go to the mess! Currently on the market we have 3 types of Micro SD cards in terms of capacity:

    Micro SD

    It is the oldest micro SD format of the three. These types of cards have a maximum capacity of 2 GB. It could be said that they are obsolete, since 2 GB today is not enough even for a 10-minute video on a modern smartphone. This format uses a FAT32 and FAT16 file system.


    Micro SDHC (HC: high capacity) cards were the next to hit the market, ranging from 2 GB capacity to 32 GB. They are compatible with SDHC and SDXC devices. SDHC cards use the FAT32 file system, so we cannot write files larger than 4GB to them.


    SDXC cards (XC: eXtended Capacity) are the third and newest generation of micro SD cards and are probably the type of card you need. These micro SD range from 32 GB of memory to 2 TB.

    Even though 2TB is the theoretical maximum of the standard SDXCthe largest micro SD cards for sale as I write this article are from 1TB micro SD. The file system they use is exFATwhich means that it does not have the limitation of 4 GB per file of the FAT format.

    As a curiosity, the largest file that can be stored on an exFAT file system is 16 EB (Exabyte), equivalent to the insane 16,000,000 TB.


    ⚠️ Important! You should know that card reviews are backward compatible with each other. That is, in a slot for micro SDXC cards, all 3 types of micro SD will work, while in a slot for micro SDHC cards, it will only be compatible with standard HC and SD. On devices with micro SD readers, only the first micro SD will work.



    When buying a micro SD or SD card you should also take into account its Class (or Class Rating). The Class, roughly speaking, indicates the minimum writing speed of a memory card. Knowing the Class we will easily know if it is fast enough for the device in which we are going to use it.

    Distinguishing the Class of a card is easy. On all SD and micro SD you will see an icon like the one below, a number inside a letter “C”.


    Sometimes the Class can be confused with the speed of the card, however a high Class does not indicate that a card is fast, it only indicates the speed of the card. guaranteed minimum speed at which the card will work, expressed in megabytes per second.

    👉🏼 See the best micro SD Class 10 on Amazon

    It has nothing to do with the maximum speed, this figure refers to the minimum speed, which will give us an idea of ​​the performance of the card or know first if it is suitable for our device.

    My advice is that, today, always look for at least one microSD Class 10Although nearly all micro SD cards on sale are now Class 10, there are still slower cards in stores.

    • class 2: minimum speed of 2 MBps/sec
    • Class 4: minimum speed of 4 MBps/sec
    • class 6: minimum speed of 6 MBps/sec
    • class 10: minimum speed of 10 MBps/sec


    Not long ago we had new classes: «V» and «A»

    Class V: Video Speed ​​Class

    In order to increase the performance of memory cards and the requirements of video recording, 4K, 8K video and 360° virtual realitythe SD Associationannounced a while ago the arrival of a new revision of the SD standard: SecureDigital 5.0

    One of the advantages of this new version is that it supports the recording of up to eight files simultaneously.

    The new SD 5.0 ​​cards are going to be called Video Speed ​​Class.


    Class V (or Video Speed ​​Class) was specially conceived to distinguish The best SD and micro SD cards to record 4K video and now also in 8K resolution.

    Class V is identified by a "V" next to a number. This figures the minimum speed of the card expressed in MB/second. The V-Class types are V6, V10, V60, and V90.

    • V6: Minimum speed 6 MB/sec. Ideal for recording videos in standard definition
    • V10: Minimum speed 10 MB/sec. Ideal for low bitrate standard definition and Full HD video recording
    • V30: Minimum speed 30 MB/sec. Ideal for recording videos in Full HD 1080p
    • V60: Minimum speed 60 MB/sec. Ideal for video recording in 4K resolution
    • V90: Minimum speed 90 MB/sec. Ideal for video recording in 8K resolution

    👉🏼 See the best Class V micro SD for video on Amazon

    I leave you this summary table so you can see at a glance the characteristics of the special memory cards for videothe Class V.


    A class: App Performance Class

    A Class A SD or micro SD memory card indicates that a card is good enough, fast enough, and reliable enough to install and run mobile apps smoothly. The App Performance Class is a relatively new terminology and they arrived with the SD 5.1 release.


    Use this kind of memory cards for tablets and smartphones will facilitate the execution of applications from the card itself.

    There are two

    • A1: minimum speed 10MB/s
    • A2: minimum speed 10 MB/s (but with more random read and write speed)


    The new class A1 SD memory cards must meet the following conditions and all manufacturers must ensure them in the devices that certify with this new specification:

    • Input/Output Operations Per Second (IOPS) – 1500
    • Write IOPS – 500
    • 10MB/s sequential sustained throughput

    Therefore, what actually certifies a Class A is the random read and write speed. It is precisely this type of reading and writing that is most used by the operating system of a smartphone, game consoles, etc., small files located throughout the card in different places.

    👉🏼 See the best Class A micro SD for Apps and smartphones on Amazon

    UHS: BUS type

    now that you know what is a Class 10, Class V or Class A memory cardlet's continue with the BUS.

    The term UHS was created in 2010, and is the way to identify the type of BUS that the memory card has. Ok, but what is the BUS? The speed at which communication between the device and the card itself can be carried out is known as BUS.

    Once the Class 10 limit was reached, the UHS (Ultra High Speed) BUS was implemented. In turn, other standards were born that we can already find today, the UHS-II and UHS-III. The BUS is represented on the card with the number inside a letter “U”.

    • UHS-I Class 1 or U1 (Ultra High Speed): minimum speed 10 MB/sec
    • UHS-I Class 3 or U3 (Ultra High Speed): minimum speed 30 MB/sec

    In this table I show you the types of BUS that exist so far, along with the maximum speeds that each one supports.


    In order to handle such a high amount of data per second (much higher than what a SATA HDD can currently handle) the micro SD UHS-II and UHS-III have a row of new pins or connectors on their back. These additional connections increase the available bandwidth to 150-300 MB/s.
    UHS-II and UHS-III memory cards are backward compatible with UHS.


    card capacity

    What capacity should I buy the card? The short answer is: It depends

    Today a 32 GB card is usually the minimum my clients are looking for. Phones with 64GB of internal storage are almost established as the standard, so the best-selling memory cards start at 64GB. They are currently the best option in terms of storage/price.

    The long answer is that the size of the card depends on the type of material you want to store and especially the quantity. If you are looking for a memory card for photography you should look for a card that stores between 1,500 and 2,000 images from whatever camera you currently have.

    Megabytes vs. Megabits

    When we talk about speed in the characteristics of memory cards we always refer to the MB/s (megabits per second). Do not confuse this measurement with Mb/s (megabits per second).

    Memory card manufacturers typically measure the speed of their cards in megabytes per second, or MB/s (or MBps, both with a capital "B"). But video recording speeds are usually measured in megabits per second, or Mb/s (or Mbps, with a lowercase 'b'). They are not the same.

    A byte is made up of 8 bits, so to go from megabits per second to megabytes per second it is multiplied by 8. Therefore, if we take the calculator we will know that 80 MB/s is equivalent to 640 Mb/s.

    Equivalence X and MB/s

    Some manufacturers use an X rating instead of MB/s. Lexar, in particular, has been using this nomenclature for many years.

    The X speed comes from the old way of measuring speed on CD-ROM and DVD drives. The standard speed of a CD-ROM drive was 150KB/s. Each X therefore equals 150KB/s.

    I leave you a table with the equivalences between X and MB/s:

    100x fifteen
    120x 18
    133x twenty
    150x 23
    200x 30
    400x 60
    600x 90
    633x 95
    1000x 150
    1400x 210
    2000x 300
    2500x 375
    2933x 440
    3000x 450
    3400x 510
    3500x 525
    3600x 540
    4000x 600
    4500x 675
    5000x 750

    How many photos or minutes of video can I store on each card?

    Suppose your new smartphone has a 12 Megapixel camera. The JPG will have an average size of 3.5 MB, therefore, for an X GB card we can store X photos:

    • 2GB – 250 approx.
    • 4GB – 500 approx.
    • 8GB – 1000 approx.
    • 16 GB – 2000 approx.
    • 32GB – 4000 approx.
    • 64GB – 8000 approx.
    • 128GB – 16000 approx.

    But if what we want is to record video, the average size of a video clip in Full HD1080p resolution at 25/30 fps, we can store X time:

    • 2GB – 2 minutes approx.
    • 4GB – 5 minutes approx.
    • 8GB – 10 minutes approx.
    • 16 GB – 20 minutes approx.
    • 32GB – 40 minutes approx.
    • 64GB – 80 minutes approx.
    • 128GB – 160 minutes approx.

    SanDisk offers us on its website this summary table of capabilities


    Best brands of SD and micro SD memory cards

    Why is the brand of a memory card important? Well, because, sadly, there are a large number of cards on the market that falsify your data and even counterfeit cards from prestigious brands.

    In this case, paying the brand is worth it. A card from a good manufacturer assures us of a certain quality and guarantee.

    Some of my favorite manufacturers are:

    • SanDisk
    • Samsung
    • Kingston
    • lexar
    • Toshiba
    • Transcend

    The cards of these brands have earned their reputation by always meeting expectations, even on many occasions delivering transfer figures higher than those announced.

    Understanding SD cards

    Just a moment! ✋❗🚫
    What do all those symbols, numbers and letters mean? 😵


    Everything we have seen during this article is reflected in the cards themselves:

    1. Maximum read speed: this is the maximum read speed of the card. It is usually expressed in megabytes per second (MB/s). Keep in mind that the speeds that the cards mark are maximum transfer peaks and are rarely able to maintain these speeds for long periods of time.
    2. This is another, perhaps old-fashioned, way of expressing maximum read speed: it is based on the read speed of audio CDs, which was 150 KB/s. To know the speed of a memory card, you just have to convert, for example, 1000x in KB/s. This is done by multiplying 150 by 1,000. The result will be given in KB, so dividing by 1000 what we do is convert KB/s to MB/s. In this case, 1000x equals approximately 150MB/.
    3. Type: this indicates the type of card. Different types of cards use different file formats and newer cards will not work in older card readers.
    4. UHS Speed ​​Class Rating: this is the card's minimum sustained write speed. This information is extremely important when looking for a card for video recording, for example. UHS Speed ​​Class 3 cards will never write slower than 30MB/s, UHS Speed ​​Class 1 cards will never write slower than 10MB/s.
    5. Speed ​​Class Rating: this is a way of classifying the oldest speed. It is redundant to the UHS speed class as it also indicates the card's minimum sustained write speed. Many card manufacturers also include it, as many consumer products still recommend products based on the older standard. A class 10 is the old speed class level and it is verified that a class 10 card will never write slower than 10 MB/s, and for example class 4 would never write slower than 4 MB/s.
    6. UHS Rating: A card's UHS rating determines the maximum bus speed at which a card can read, assuming the memory on the card is fast enough to match. Non-UHS cards have a maximum of 25 MB/s, while UHS-I cards support up to 104 MB/s. UHS-II cards support up to 312 MB/s. Both the card reader and the card must support the same standard to benefit from the speed boost, but UHS cards are backwards compatible with older readers, they just won't be as fast on them.
    7. Ability: this numbering indicates the capacity of the card. SD cards range up to 2 GB, SDHC cards range from 2 GB to 32 GB, and SDXC cards from 32 GB to 2 TB.

    How does a micro SD card work?

    SD cards have many advantages over other storage systems.

    Micro SD cards differ from other flash memory because they can be written to thousands of times without being damaged. Another advantage is that they do not need power to maintain the data (non-volatile memory). On the other hand, other memories such as RAM do need energy (volatile memory).

    They are reliable and ideal for portable devices because they have no moving parts, like SSDs, so there is no risk of data loss from shock or vibration.

    In other words, in a way, they are like small SSDs, albeit with lower performance.

    The above features make them ideal for use in smartphones, digital cameras, and other devices that need portability, ample storage space, and ruggedness.

    As with SSDs, data on an SD card is stored on a series of electronic parts called NAND chips.

    These circuits allow data to be recorded and stored on the memory card. And since there are no moving parts, data can be transferred at high speeds to and from the card, far exceeding the speeds of CD/DVDs or HDDs.

    history of sd cards

    If we go back to the beginning, everything was born from the hand of Toshiba when at the end of the 80's it launched the architecture NAND for memories. Without a doubt, this was the seed of a great revolution in the world of information storage.

    buy-best-sd-cardIt was not until 1997 when Siemens and SanDisk teamed up to design the MMC or Multimedia Media Card, a 24 mm x 32 mm x 1.4 mm card that originally used a 1-bit, 7-pin serial interface. There were several issues that made it popular on a large scale. On the one hand, its characteristics and dimensions, and on the other, the fact that companies did not have to pay royalties if they wanted to add a card MMC to your products. Perhaps this was the determining factor.

    Meanwhile, in the field of portable storage, Sony launched its well-known Memory Stick, Olympus and Fujifilm developed the XD-Picture Card and Toshiba created the Compact Flash. All these cards and technologies coexisted for years. Each manufacturer opted for a standard, however, and over the years the SD format was the clear winner and prevailed over the others as the storage standard.

    SD card is born

    It seems like yesterday, but the card standard SecureDigital You are of age. It was launched in the market in 1999 and was developed by various companies including SanDisk, Panasonic and Toshiba. Today the standard is in charge of the SD Association (SDA).

    Comparison of sizes between SD and MicroSD card

    Taking into account their size, we can find 3 types of SD memory cards, although some have already fallen into disuse:

    • SD: It was the first to be launched on the market. Its dimensions are 32 millimeters high x 24 millimeters wide.
    • Mini SD: the second evolution, and almost extinct now, has dimensions of 21.5 millimeters high x 20 millimeters wide x 1.4 millimeters thick. Its weight is 0.8 grams.
    • Micro SD: without a doubt the most popular format. Its dimensions are 15 millimeters high x 11 millimeters wide x 1 millimeter thick. Its weight is 0.3 grams.

    The first SD for sale

    Sandisk SD card

    A year after its launch, in the year 2000 the first models available in 32 MB and 64 MB go on sale. Today we would hardly keep a couple of photos in them, but they were a great advance for their time. Its dimensions are 24 mm x 32 mm x 2.1 mm and its approximate weight is 2 grams. It has 9 pins and mechanical write protection. Its operating voltage varies between 2.7 and 3.6 v.

    Did you know that the SD card logo is a variant of the logo that Toshiba introduced for the DVD?

    Mini SD: an announced failure

    Mini SD cardIn 2003, SanDisk presented at CeBIT 2003 a smaller standard compared to the SD original. The card comes out miniSD. With a size of 20 mm x 21.5 mm x 1.4 mm and 1 gram in weight, the SD Card Association or SD Association (SDA) recognized it that same year as a reduced size extension for the card standard. SecureDigital. Loses the write lock to the original SD and its input voltage. operation is maintained at 2.7 and 3.6 v. Despite this, the manufacturers did not opt ​​for this format and this version was considered a failure.

    Micro SD: the current standard

    buy-best-micro-sd-cardHowever the case of Micro SD (also called T-Flash, TF or TransFlash) it was different. This format was born in July 2005 by SanDisk with about 15 long × 11 wide × 1 millimeters thick and weighing only 0.8 grams.
    The first models had capacities of 8, 16, 32, 64 and up to 128 MB. The great demand for digital content storage drives the creation of a new format: the microSD SDHC (High Capacity). But the need to increase the current speed rates of the time and the size of the memories later gave rise to the microSD SDXC (eXtended Capacity), with its up to 2 TB of capacity and a Bus that reaches breakneck speeds, even higher than that of SATA hard drives and close to 300 MB/sec. Time established this card as the current storage standard.

    SD Express: the future

    SD-Express-SDUCThe future goes through the SDUC or SD Express. This revision corresponds to SD 7.0 and is expected to hit the market in the first quarter of 2019. Some voices place them as substitutes for current SSDs due to their maximum capacity of 128TB and transfer speeds of up to 985 Mb/sec.

    If you want to learn more about SDUC and MicroSD Express, take a look at our article on SD Express cards.

    Evolution of SD or Secure Digital cards

    Over the years, a number of different SD cards have evolved in parallel:


    WiFi SDIO SD CardUnlike traditional SD, the standard SDIO it was not designed to store information, but to be a type of connection that allows information to be transmitted. It keeps the same size as the SD card and allows you to integrate small accessories, such as GPS receivers, Wi-Fi or Bluetooth adapters, modems, barcode readers, IrDA adapters, FM radio tuners, RFID readers or digital cameras.

    Integration with other devices such as RS-232 serial adapters, TV tuners, fingerprint scanners, magnetic stripe readers, Bluetooth/Wi-Fi/GPS, ethernet adapters and PCS, CDPD, GSM modem adapters, etc. has been proposed. . but have not yet been implemented.

    Wi-Fi SD Cards

    Wi-Fi Eye-Fi SD CardThe best known Wi-Fi SD cards are without a doubt the EyeFi. These cards of up to 8GB capacity have the particularity that they integrate a Wi-Fi chip inside, so that together with a Software it allows to communicate wirelessly and directly with other equipment such as PC's, laptops, tablets or smartphones, and thus provide of Wi-Fi connectivity to the cameras where they are used. The new Eye-Fi Mobi Pro adopts the standard SDHC and are available in 16 and 32 GB. The Eye-Fi Pro X2, the first SD card with 802.11n WiFi.

    Other manufacturers such as Toshiba also launched SD cards with Wi-Fi connection, the Toshiba FlashAir, and 3 units of 16, 32 and 64 GB respectively are available in their catalog.

    SD Cards vs. Compact Flash

    Traditionally, SD cards were always just a few steps behind Compact Flash cards in performance, but since Compac tFlash cards haven't been updated in a while, SD cards recently overtook them with UHS-II cards.

    UHS-II SD cards offer read speeds of up to 312 MB/s, nearly twice the speed of UDMA 7 CompactFlash cards. However, because they are so new, not many cameras and card readers support UHS-II cards, and while UHS-II cards are backward compatible, they will not work at full speed with card readers. oldest. In fact, most high-end DSLRs still can't write at UHS-II speeds.