Why is my SD card so slow? [A Comprehensive Analysis for 2024]

Firstly, there can be numerous reasons for a slow SD card, such as an old USB port, a slow card reader, a sluggish computer, or outdated SD card drivers. To fix a slow SD card or make it run faster, you can try switching to a different card reader, optimizing the card's performance, formatting the storage card, or updating the SD card driver.

In this article, we will explain in detail the reasons that cause an SD card to become slow and let you know how to fix and avoid the issue.

Why is my SD card so slow?

There are many reasons why an SD card might transfer slowly to a computer, and most of them have little to do with the speed of the SD card itself. However, that is a possibility, so we'll start there.

1. Slow SD Card

Original SD cards had no extra labeling, just “SD.” SD cards are classified by size and speed:

From this chart, you can clearly see the speed class of your SD card. However, these numbers are theoretical and don't necessarily reflect real-world performance. An SD card should be able to reach these speeds in theory, but its speed is also limited by other factors like the bus speed rating. When buying an SD card, pay attention to its advertised speed and interface requirements.

If you want to know which class your SD card belongs to and what kind of usage scenarios it is suitable for, you can click on the link below to learn more.

2. Slow SD Card Reader

If you have a fast SD card but use a slow SD card reader, such as one limited to 70 MB/s, your card won't perform at the advertised speeds.

So you must make sure that your reader supports the USB standard that you're using. And, of course, it must support the SD card standard that you're using.

3. Old USB port

Assuming you have a fast SD card and reader, the next factor to consider is your USB port. Here are the release years and associated speeds for different USB generations:

From the chart, you can see that any computer manufactured before 2011 will have USB 2.0 at most. Check if your laptop or desktop was released in 2011 or earlier; this could be the reason for the slow transfer speeds.

However, if you're using an old USB 2.0 hub plugged into a USB 3.1 port, your transfer speeds will be limited to USB 2.0 speeds. So if you find that your card reader is slow when used with a hub, try plugging it directly into your computer to see if the SD card's speed improves.

As you can see, to get the full speed out of a USB port, both the SD card, the card reader, the cable, the USB hub (if used), and the USB port on your computer must all support the same maximum speed.

4. Slow SSD/HDD performance on your computer

Even if you have the fastest USB port, cable, reader, and SD card in the world, once all that data is downloaded to your computer, it still has to be saved to an HDD or SSD. So if your computer's storage is slow, the transfer will still be slow.

To resolve this issue, you'll need to install a faster solid-state drive (SSD), typically an NVME SSD, on your computer. Additionally, if your SSD is also slow, you can follow the link below for further assistance:

5. Hardware failure/Old drivers

In rare cases, your SD card might be slow because of an outdated driver. Usually, Windows will install the correct driver for you automatically. You can update the SD card driver manually to fix this issue.

It could be a damaged cable, or a faulty USB port on your computer. Try plugging the device into a different port, a USB hub, or a different computer to see if that solves the problem. Hardware failures can cause other issues as well, which you can read about in the link below:

Why Is My SD Card Suddenly Blank | How to Fix It?

So, in this article, I will explain to you in detail how to fix a blank SD card without losing data and how to handle an SD card safely. Keep reading for more information!

6. Large Files

SD cards typically have a maximum read speed of 300 MB/s during writing, so this can take a long time if your files are very large. In this case, you might use an SSD with faster read-write speeds or back up large files instead.

Now that we've looked at several reasons why an SD card can become slow, how do you test the speed of an SD card? The next section will reveal how.

To figure out the speed of your SD card, you can follow these steps: 1. Check the SD card packaging: Most SD cards will display their speed class on the packaging. Common speed classes include Class 4, Class 6, Class 10, UHS-1 Class 1 (U1), and UHS-1 Class 3 (U3). These classes indicate the minimum write speed, for example, Class 10 means a minimum write speed of 10 MB/s. 2. Use a card reader and computer: Insert the SD card into a card reader, then connect the reader to your computer. Open "My Computer" or "File Explorer," locate the SD card's drive, right-click it, and select "Properties." Under the "Tools" tab, click "Start Check." While this is mainly for error checking, it can also give you a rough idea of the SD card's read and write speeds. 3. Use specialized software: Download and install a speed testing tool like CrystalDiskMark, HD Tune, or ATTO Disk Benchmark. Run the software, select the SD card as the target, and initiate the test. These tools will display specific read and write speed numbers. 4. Visit the SD card manufacturer's website: Go to the official website of the SD card manufacturer, find the exact model you're using, and you'll typically see the advertised speed ratings. Keep in mind that actual speeds in use may vary due to device performance, file size, sequential/random reads/writes, and other factors, so test results might differ slightly from the advertised speeds.

Since SD cards vary in speed, it can be difficult to know exactly how fast your SD card is. This section will teach you how to get the maximum read and write speeds of an SD card as well as its random read and write speeds. We recommend using a reliable third-party tool – AOMEI Partition Assistant Professional. It can help test the speed of your SD card and display clear test results: sequential read and write speed, random read and write speed, latency, and I/O.

Please download this app on your computer and follow the instructions below:

Step 1: Launch AOMEI Partition Assistant. Then click the Download button to activate the "DiskMark" feature under "Discovery".

Step 2. Select the target drive, test data, and block size from the drop-down menus.

Step 3: Once all settings are configured, click “Start” to begin the disk test. You'll then see the sequential or random read/write speeds, I/O, and latency data.

The bottom line?

Typically, SD cards or memory cards have slower read and write speeds than other external data storage devices.

A slow SD card can be the result of speed class limitations, hardware failure, large file storage, and outdated card drivers. When your SD card is slow, it will have decreased read and write speeds, and it can take a long time to open any files stored on the card. This article will explain these reasons in detail. Click the Share button below if you'd like to send this article to someone else.

Why is my SD card so slow? FAQ

Do you know why your SD card is running slow? Here are some questions and answers to help you understand the issue better.

1. How long does an SD card last?

Around 10 years. SD cards store information on flash memory, which, under normal use and with current technology, can last for a decade or more. There is no need for consumers to upgrade their SD cards frequently to reduce e-waste.

2. How can I make my SD card faster?

The slow SD card issue can be addressed through the following solutions:

• Replace the card reader
• Format the SD card
• Update the SD card driver
• Optimize SD card performance
• Clean up junk files on the SD card

3. Why is my SD card so slow?

You might try these and see if they help.

I suggest that you run the Hardware and Devices troubleshooter.

Open the Control Panel > Click on Troubleshooting > Choose Hardware and Devices to run the troubleshooter.

You can also resolve this issue by installing the latest drivers from the manufacturer's website.