Bit Buddy Guides

Understanding SD Card Types and Classes

Break down the sometimes confusing world of SD cards into bite-sized pieces.

Ever stared at a wall of SD cards at a store and felt overwhelmed by all the options? You're not alone. Let's break down the sometimes confusing world of SD cards into bite-sized pieces.

Physical Sizes: The Big Three

Standard SD Cards

  • The original and largest size (32 x 24 x 2.1mm)
  • Most common in DSLRs and video cameras
  • Easier to handle but becoming less common in newer devices
  • Maximum capacity: up to 2TB (theoretically)

miniSD Cards

  • Middle child of the SD family (21.5 x 20 x 1.4mm)
  • Relatively rare these days
  • Mainly found in older mobile devices
  • Maximum capacity: up to 4GB
  • Largely obsolete but worth knowing about

microSD Cards

  • The tiny powerhouse (15 x 11 x 1mm)
  • Most popular format today
  • Used in phones, action cameras, drones
  • Can be used in larger slots with adapters
  • Maximum capacity: up to 2TB (theoretically)

Capacity Categories

SD (SDSC - Secure Digital Standard Capacity)

  • The original format
  • Up to 2GB capacity
  • Mostly obsolete now
  • Still found in some older devices

SDHC (Secure Digital High Capacity)

  • 4GB to 32GB
  • Widely supported
  • Great for everyday use
  • Perfect for most cameras

SDXC (Secure Digital Extended Capacity)

  • 64GB to 2TB
  • Uses exFAT file system
  • Higher price point
  • Ideal for 4K video and pro photography

SDUC (Secure Digital Ultra Capacity)

  • Up to 128TB (theoretical)
  • Newest specification
  • Not widely available yet
  • Future-proofing option

Speed Classes: The Need for Speed

Original Speed Class

Marked with a circle and number:

  • Class 2: 2MB/s minimum write speed
  • Class 4: 4MB/s minimum write speed
  • Class 6: 6MB/s minimum write speed
  • Class 10: 10MB/s minimum write speed

UHS Speed Class

Marked with a U and number:

  • U1: 10MB/s minimum write speed
  • U3: 30MB/s minimum write speed

Video Speed Class

Marked with a V and number:

  • V6: 6MB/s minimum write speed
  • V10: 10MB/s minimum write speed
  • V30: 30MB/s minimum write speed
  • V60: 60MB/s minimum write speed
  • V90: 90MB/s minimum write speed

Application Performance Class

Marked with an A and number:

  • A1: 1500 random read IOPS, 500 random write IOPS
  • A2: 4000 random read IOPS, 2000 random write IOPS

Specialty Cards

Industrial SD Cards

  • Built for extreme conditions
  • Extended temperature ranges
  • Enhanced durability
  • Used in industrial equipment
  • Usually more expensive

WiFi-Enabled SD Cards

  • Built-in wireless capabilities
  • Transfer files wirelessly
  • Some can create mini networks
  • Example: Eye-Fi cards

Pro-Grade Cards

  • Extreme write speeds
  • Better build quality
  • Enhanced reliability
  • Error correction
  • Usually from premium brands

Common Use Cases

Photography

  • SDHC/SDXC
  • Class 10 minimum
  • U3/V30 for 4K
  • V60/V90 for 8K

Mobile Devices

  • microSD format
  • A1/A2 class recommended
  • Class 10 minimum
  • SDHC/SDXC depending on needs

Dashcams/Security Cameras

  • Industrial grade recommended
  • High endurance cards
  • Continuous recording optimized
  • Temperature resistant

Gaming

  • A1/A2 class for best performance
  • microSD format usually
  • Class 10 minimum
  • SDXC for large game libraries

Compatibility Tips

  • Newer cards may not work in older devices
  • Cards above 32GB usually need exFAT support
  • Speed class requirements vary by device
  • Always check device specifications
  • Adapters can affect performance

Future Trends

  • Increasing capacity limits
  • Faster transfer speeds
  • More focus on application performance
  • Enhanced durability
  • Better power efficiency

Remember: Always check your device's manual for compatibility before purchasing any SD card. The fastest, highest-capacity card isn't always the best choice - match the card to your specific needs and device capabilities.