SD Card Symbols - A Guide to Understanding Your Memory Card
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SD cards, or Secure Digital cards, are a vital form of flash memory storage used across a wide range of digital devices, from cameras and smartphones to laptops and gaming consoles. They are crucial for storing vast amounts of data in a compact, portable format, making them essential for digital photography, videography, mobile computing, and beyond. Understanding the symbols on SD cards is crucial for users to select the right card for their specific needs, ensuring compatibility, optimal performance, and sufficient storage capacity.

Common SD Card Symbols and Their Meanings

Memory cards vary in configuration and size, designed for different storage needs and performance. SD cards come in various types like SD, SDHC, SDXC, and SDUC, all sharing the same size but varying in capacity and speed. This range lets users choose a card matching their device’s needs, from basic phone storage to handling 4K and 8K video recording in cameras and drones. Knowing these differences is key to picking the right card for your tech needs and budget.

Speed Class

The speed class of an SD card is a key indicator of its minimum write speed, which is vital for tasks like video recording or high-res image capture. The standard speed classes are:

  • Class 2: Minimum write speed of 2MB/s. Suitable for standard definition video recording.
  • Class 4: Minimum 4MB/s write speed, perfect for HD video recording and continuous shooting with digital cameras.
  • Class 6: This SD card offers a minimum write speed of 6MB/s, ideal for recording high-resolution videos.
  • Class 10: Minimum 10MB/s write speed, perfect for full HD video recording and high-res photos.
SD Card Symbols Explained

UHS (Ultra High Speed) Speed Classes

UHS Speed Classes were introduced to support higher write speeds. These are denoted as U1 and U3:

  • U1: Minimum write speed of 10MB/s, equal to Class 10, perfect for HD photography and video recording.
  • U2: Not commonly used, but with a minimum write speed of 20MB/s.
  • U3: A minimum writing speed of 30MB/s, perfect for capturing top-notch 4K videos and continuous rapid shooting in high resolutions.

Video Speed Classes

The latest addition to SD speed classes, designed specifically for video. These include:

  • V6: With a minimum write speed of 6MB/s, suitable for higher-quality video recordings.
  • V10: Minimum write speed of 10MB/s, ideal for full HD recordings.
  • V30: Offers a minimum write speed of 30MB/s, suitable for real-time broadcasts and recording in 4K.
  • V60: Optimized for recording high-resolution 4K video at high frame rates with a minimum write speed of 60MB/s.
  • V90: The highest video speed class at a minimum write speed of 90MB/s, capable of handling 8K video recording and other demanding video modes. 

Understanding these speed classes is vital for users to ensure their SD cards can handle the specific tasks they’re intended for, from basic video recording to high-end professional photography and videography.

Bus interface

The bus interface symbol “U” or “I” shows the highest data transfer speed between the SD card and the device, which is crucial for fast data transfer in high-res cameras. The most common symbols are:

  • UHS-I – Provides a maximum transfer speed of 104MB/s.
Symbols on SD Cards and their meaning
  • UHS-II – Offers a maximum transfer speed of 312MB/s, making it ideal for high-end cameras and devices that require fast data transfer rates.
  • UHS-III – The fastest interface with a maximum transfer speed of 624MB/s, suitable for professional-grade cameras and recording equipment.
Symbols on SD Cards and their meaning

Understanding SD Card Types

When choosing an SD card, understanding the symbols for its memory type and capacity is key. The primary types are SDSC (Standard Capacity), SDHC (High Capacity), and SDXC (Extended Capacity). Each symbol represents a distinct capacity, helping you choose the correct card. Understanding these variances enhances your buying choice, and they are vital for expanding storage on digital cameras, smartphones, and other devices.

  • SD (Secure Digital) – SD cards offer up to 2GB of basic storage, ideal for documents, small photo collections, and low-res videos.
  • SDHC (Secure Digital High Capacity) – 2GB to 32GB SDHC Cards are perfect for high-res photos and HD video, holding more data than regular SD cards.
A Guide to Speed Classes for SD and microSD Cards
  • SDXC (Secure Digital eXtended Capacity) – SDXC Cards ranging from 32GB to 2TB are perfect for professional photography, 4K video, and large data storage needs, offering ample space for high-res media and files.
  • SDUC (Secure Digital Ultra Capacity) – SDUC cards mark the latest in SD technology, offering 2TB to 128TB of storage. They’re built for future needs like 8K video and VR applications.

Knowing an SD card’s storage capacity is key to having enough space for your data without overspending on unnecessary storage. Also, verify your device’s compatibility with different SD card types, as not all formats are supported by every device.

SD Card Symbols Explained

Application Performance Class

The Application Performance Class denoted as A1 and A2, is crucial for users who store and run apps on their devices, such as smartphones and tablets. These classes indicate the minimum random read and write speeds, ensuring smooth app operation directly from the SD card.

  • A1: Minimum random read SD Card of 1500 IOPS (Input/Output Operations Per Second) and minimum random write of 500 IOPS. This class is designed to improve app performance, making it suitable for mobile devices where apps are frequently used.
  • A2: Offers even higher performance, with a minimum random read of 4000 IOPS and a minimum random write of 2000 IOPS.
Symbols on SD Cards Explained

A2 cards significantly improve app loading and running directly from the SD card, suitable for intensive app usage and faster data access.


Understanding SD card symbols and classes is essential for choosing the right card. Factors like speed, storage, device compatibility, and app performance drive purchase decisions. Whether for basic data storage or high-end professional use, choosing the right SD card ensures optimal performance and user satisfaction.

Memory cards, despite their convenience, are susceptible to data corruption, just like any other storage device. If you encounter problems with your SD card, it’s crucial to seek professional help immediately. PITS Global Data Recovery Services offers reliable and swift SD card data recovery solutions to ensure your valuable data is retrieved safely. Contact us for expert SD card recovery services and secure your digital memories today.

Frequently Asked Questions

SD cards are vital for transferring and storing data across many electronic devices, such as cameras, smartphones, and tablets. They offer a reliable method of keeping data safe and accessible, making them popular among tech users. Whether you’re a professional photographer or want to increase your device’s storage, understanding SD card benefits can improve your digital experience.

There are three primary types of SD cards: SDSC (Standard Capacity), SDHC (High Capacity), and SDXC (Extended Capacity). Each type has different storage capacities and is used for various purposes.

Class 4 SD cards have a minimum writing speed of 4MB/s, making them suitable for basic photo and video storage needs. They are not recommended for high-resolution photos or HD video recording.

UHS-I and UHS-II refer to the bus interface of an SD card, indicating the maximum transfer speed between the card and a device. UHS-II offers faster speeds than UHS-I, making it suitable for high-end devices that require fast data transfer rates.

Class 10 is a speed class for SD cards, offering a minimum data transfer rate of 10 MB/s. This makes it ideal for high-data use, such as capturing high-resolution photos and recording HD video. Its ability to handle large files quickly makes it recommended for photographers, videographers, and digital content creators who need efficient storage that matches the speed of modern cameras and recording devices.