How to read numbers and codes from a memory card

Learn to fully read the memory cards you use with this guide in which we explain the meaning of all the numbers and codes they have.

Memory cards are those small accessories that are used to expand the storage of technology devices such as mobile phones, photo cameras or video cameras.

They started out as a luxury accessory, but their price was significantly reduced and they are now accessible to any user. Without going any further, it is very likely that you also have a memory card at home. Do you know what its main characteristics are?

Perhaps you have memory cards that you have not used for a long time and for which you lack any information. You don't know what capacity they have, what is its reading speed or just what type of memory card it is. If so, you don't have to worry, because with this guide you will learn how to read the numbers and codes on your memory card to fully know all its characteristics.

Memory card

This is all you need to know to read the numbers and codes on your memory card.

How to read numbers and codes from a memory card

If you analyze your memory card well, you will find different terms difficult to decipher. Taking as an example the model in the image above, we see that it says the following: SanDisk Extreme, 128 GB, microSD, XC, V30, A2 ... What does this all mean?

It's easy, each of these terms refers to the main characteristics of your card, which we will talk about one by one below.


One of the terms that appears highlighted more strongly on the card is the name of the manufacturer of the card. In our example the brand is SanDisk, although the memory cards can be from other brands such as Kingston, Trascend or Samsung.

Card types

Another term that you will surely find informs you about the type of memory card you have. In summary, the card can be of two types: Compact Flash and SD (Secure Digital).

On the one hand, Compact Flash cards can be Type I or Type II. On the other hand, SD memory cards can be simply SD, microSD or MiniSD, which was not very successful in the market. If you look at your card, you will see that it says Compact Flash, SD or microSD, as is the case with the model we have taken as an example.

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Memory capacity

Very important is also the number that refers to the capacity of the card. We could say that it is the most relevant of all of them, because when we use these cards what matters mainly to us is the memory that we are going to add to the device in which we are going to use it.

The memory capacity of a card is represented in gigabytes and can be very varied: 32GB, 64GB, 128GB, 256GB ... Obviously, the more capacity the card has, the more expensive it will be.

SD cards also represent their capacity using the terms SC, HC and XC, which mean the following:

  • SC: Standard Capacity, up to 2 GB of memory.
  • HC: High Capacity, up to 32 GB of memory.
  • XC: Extended Capacity, up to 2 TB of storage.
MicroSD XC memory card

Example of microSD XC memory card.

Read and write speed

Another of the codes that you will see on your memory card is the one that refers to the writing speed, also one of the characteristics that you should give the most importance to when buying a new model. It's about the speed at which the card can store the information. The higher that speed, the more information you can save in less time.

On some cards you will find the write speed directly, for example 50MB / s. This figure refers to the maximum speed that the card can reach, but not to the speed known as "minimum maintained", which is usually reflected in the form of different codes depending on the type of card.

First of all, we must mention that Compact Flash cards use a terminology Ultra Direct Memory Access (UDMA), which ranges from 0 (16.7 MB / s) to 7 (167 MB / s).

On the other hand, in SD memory cards you will have to attend to the concept "Class" to find out what your writing speed is, plus take into account the bus -data transfer system-. The different classes of an SD card are as follows:

  • Class 2 (C2): 2MB / s minimum write speed.
  • Class 4 (C4): 4 MB / s minimum write speed.
  • Class 6 (C6): minimum write speed of 6MB / s.
  • Class 10 (C10): minimum write speed of 10MB / s.

These speeds were insufficient for SD cards, so the UHS (Ultra High Speed) standard class I and II, resulting in UHS-I, UHS-I II, SDHC I, SDHC II, SDXC I and SDXC II cards. If we look at the SanDisk card that we have chosen as an example, we can see that it is SDXC I.

In addition, these types of cards use another term to indicate their minimum maintained write speed. They can be the following:

  • Ultra High Speed ​​Class I (U1): 10 MB / s minimum write speed, but better data transfer system than Class 10.
  • Ultra High Speed ​​Class 3 (U3): minimum write speed of 30MB / s.

If you look closely at the example model in this guide, you will see that the code "V30" also appears, do you know what it refers to? Well, this term is related to the video speed, so you are especially interested if you use the memory card on camcorders. You can find the following codes:

  • Class V6: Video recording in HD resolution at 72p.
  • Class V10: video recording in Full HD resolution at 1080p or lower.
  • Class V30: video recording in 4K resolution at 24 or 30 fps.
  • Class V60: video recording in 4K resolution at 60 or 120 fps.
  • Class V90: video recording in 8K resolution at 60 or 120 fps.

It is also important to know that on some memory cards reading speed is indicated of the same, which is represented with codes such as "X300", "x600" or "x1000". The higher the amount, the faster the reading speed of your card.

Meaning codes and numbers of memory cards

These are the meanings of the different codes and numbers on a memory card.

Compatibility with the installation of apps

From Android 6, users have the possibility to install applications directly on the microSD cards inserted in the mobiles. However, it was not the best possible option, as most microSDs were not designed for this function and ended affecting terminal performance.

For this reason, in August 2019 the first class A1 and A2 microSD memory cards came on the market, created specifically for Android users to be able to install apps directly on them without affecting the performance of the phone.

Both class A1 and A2 cards support high reading and writing speeds, with the minimum sustained speed of both 10MB / s. Therefore, if you are going to use a microSD card in your mobile, make sure that it has this specification.

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Finally, another aspect that you should look at before buying a memory card is its resistance and durability. This data is not reflected on the card itself as such, so if you have one at home and want to know its resistance level, you should go online to find out the information offered by the manufacturer in this regard.

Brands often test the durability of their cards by testing them under the toughest conditions. For example, in the case of our example, SanDisk specifies that it is resistant to high temperatures, water, X-rays and shock.

In this way, you will know that you can use the memory card continuously without fear that get easily damaged and lose data that it stores.

So far our guide on the meaning of numbers and codes that make up a memory card. You have already seen that at first they seem like a series of nonsense terms, but that with a little theory they help you easily know the most important features from your memory card.

Related topics: Mobile, Technology

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