What do the A1 and A2 ratings on SD and microSD cards mean? (2023)

You may have seen new A1 and A2 speed ratings on some of the newer SD and microSD cards. So what do they mean? And when should you find out about it?

You may have seen new onesA1eA2Speed ​​ratings on some of the new SD and microSD cards. What are they referring to and should you pay attention to them?

In short, when choosing a memory card for something like a camera, you can safely ignore the A rating and focus on speed ratings that start with a V or U.

(Video) SD and microSD Card Specification Labels Explained – DIY in 5 Ep 141

When using the card in a smartphone or gaming device, the A rating is much more useful.

A1 and A2 SD card ratings explained

SD and microSD cards had several different speed rating categories. You see them in those little symbols and numbers on the cards and on their packaging.

First there was the speed class, ranging from class 2 to class 10. Then there was the UHS speed class, where cards fell below either U1 or U3. More recently, there is a newer system, Video Speed ​​Class, which uses categories like V30, V60, and V90.

These are all categories where the card meets or exceeds a minimum sustained sequential write speed threshold. Basically, this means that they can keep track of a certain amount of data that is written to them all the time. The obvious case where this comes into play is when shooting high-definition (and ultra-high-definition (UHD)) video. The higher the quality and bitrate the camera wants to record, the faster the card needs to be to keep up with the stream of data coming at it. Therefore use a very slow card in a4K or 5K camera like a GoProcauses locking and writing to stop - the card just can't keep up. What's worth noting is that the actual speed you see in practice also depends a lot on what device you're using it on, e.g. B. a camera, a smartphone or another mobile device. In practice, the slowest link in the chain determines the maximum speed you get. Just because you have a really fast memory card doesn't necessarily mean you'll see faster performance in practice.

Until now, recording media such as video, photos and audio have been the main market targeted by SD and microSD cards. Therefore, speed rating systems have reflected this emphasis on high definition video recording.

(Video) Should you get an A2 class sd card? Raspberry Pi 4 8GB. A1 Vs A2. Application Performance Class.

But more and more memory cards are used to extend the storage of devices running applications. Devices such as smartphones and mobile game consoles. Applications running on these devices interact with disk space differently. Instead of a sequential stream of data, they want to write multiple small chunks of data whenever space is available. This is called random read/write (as opposed to sequential read/write, which is important for video).

As you can clearly see in theSpeed ​​test results I posted, a card that is fast for sequential reads and writes is not necessarily fast for random reads and writes. Just because a card can record 4K or even 8K video at a very high bitrate doesn't necessarily mean it's suitable for the different types of applications that might be required.

With this in mind, the SD Association has released a new rating system specifically designed to categorize the suitability of SD and microSD cards for heavy application use. It is known as theApplication performance class specification, and is written in the form of A1 or A2. The idea behind this is that if you use an SD or microSD card to run apps on your mobile device, you can be sure that a particular card is suitable before you buy it and hopefullyreduce frustrationof users blindly buy cards that are simply not suitable for running applications.

So far there are only two designated classes: A1 and A2. The SD Association will add more as needed. The thresholds for meeting these categories are:


to display theA1symbol, a card must meet or exceed these limits:

(Video) SD Cards Explained! What do all of those symbols mean ? How to choose the right one for you.

  • Random read: 1500 IOPS
  • Random write: 500 IOPS
  • Continued Sequential Write: 10 megabytes per second


For theA2category, should at least be able to:

  • Random read: 4000 IOPS
  • Random write: 2000 IOPS
  • Continued Sequential Write: 10 megabytes per second


The "IOPS" here means input-output accesses per second. It's a different metric from what we're used to from memory cards, where speed is typically measured in megabits per second or megabytes per second, depending on how video bitrate is measured and what visual media is recorded on the card. However, the IOPS metric is more meaningful for measuring the types of operations that applications are performing.

You'll also notice that the specification also includes a minimum requirement for sequential writes. The 10MB/s limit equates to a Class 10 video speed rating, which is too slow for many of today's cameras that capture 4K, 5K, or 8K video.

Is the application performance class specification relevant for digital cameras?

The truth is. At least not yet. As mobile cameras eventually evolve into more app-loaded devices, maybe one day that will become more relevant. But we're not there yet.

It should also be noted that the A rating is a rating system parallel to the V and U systems. By that I mean it doesn't replace them, and it's entirely possible - even likely - to have a card that's both rated A1 and V30, or A2 and V90. They refer to two different things.

(Video) A1 vs A2 sd card explained in hindi #A1vsA2 #microsdcard

Memory card tools

Here are some other related tools I've gathered that might be helpful when working with memory cards and data rates.

Convert Mbps to MB/s and Speed ​​Rating X to MB/s

Another related and common calculation that often needs to be performed when working with memory cards is to convert the video bitrate measurement convention (Mbps, Mb/s, or megabits per second) to the memory card speed measurement convention (MBps, MB/s). s or megabytes per second).

So I put together a simple calculator for that separately. You can find it here:

  • Convert megabits per second to megabytes per second calculator
  • Convert memory card X speed rating to MB/s

Memory card size calculator

When figuring out what size memory card to buy, it can be helpful to know how much camera video fits on a card. Here are some tools that might come in handy for this:

  • Video bitrate and memory card size calculator
  • How much 4K video can 128GB hold?
  • How much 4K video can 256GB hold?
  • How much 4K video can 64GB hold?

Working with memory cards

Here are some related posts on understanding memory cards and working with them.

(Video) What are those symbols on SD cards?

  • Fastest SD card speed tests.As cameras gain enhanced 4K, 5K, and even 8K video recording capabilities and constant continuous recording, some of them require the write speeds that only the fastest SD cards can provide. So here's a rundown of the fastest SD cards based on my independent testing.
  • Fastest MicroSD card speed tests.Need a fast microSD card? Whether you're shooting 4K, 5K, or 8K video, high-speed burst photos, or other demanding applications, speed matters. These are the results of my independent speed tests of the fastest microSD cards.
  • Types of SD cards explained.There are different types of SD cards, as well as different speed rating systems and cryptic codes. Here is a summary of the differences.
  • .Wondering what is the difference between UHS-I and UHS-II in SD and microSD cards? Here's an explanation.
  • What are the A1 and A2 ratings for SD and microSD cards?You may have seen new A1 and A2 speed ratings on some of the newer SD and microSD cards. So what do they mean? And when should you find out about it?
  • .Here's a guide to using the SD Association's official SD card formatter to prepare your SD and microSD cards for use.
  • How to format SD card on Mac.Here is a step-by-step guide on how to format SD and microSD cards.
  • Best Free SD Card Data Recovery Software.Here is an overview of the best free data recovery software that you can use if you accidentally deleted photos or videos from your SD card.
  • How to remove deleted photos from Rover SD card: SD card recovery options.All the photos you took are gone from SD card. The good news is that there are still good chances to recover photos from SD card. Here's what to do. Contains both free and paid SD card recovery options.


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