microSD vs. SD Speed Classes
Comparing 2 standards across 13 specifications. 13 key differences identified.
microSD (originally developed as TransFlash / T-Flash by SanDisk in 2004 and ratified by the SD Association in 2005) is the ultra-compact form factor of the Secure Digital family. Measuring 15.0 × 11.0 × 1.0 mm (approximately 20% the size of a standard SD card), it is the universal removable storage medium for smartphones, action cameras, drones, and handheld gaming consoles.
SD Speed Classes are standardized performance metrics defined by the SD Association to guarantee minimum sustained write speeds for uninterrupted video recording and random IOPS execution for applications. They encompass legacy Speed Class (C2–C10), UHS Speed Class (U1/U3), Video Speed Class (V6–V90), and Application Performance Class (A1/A2).
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Body
|
SD Association (SDA) | — |
|
Original Name
|
TransFlash (TF Card / T-Flash by SanDisk, 2004) | — |
|
Physical Dimensions
|
15.0 mm × 11.0 mm × 1.0 mm (Weight: ~0.25 g) | — |
|
Pin Configurations
|
8 pins (UHS-I / Legacy) / 16 pins (UHS-II dual-row) | — |
|
Capacity Standards
|
microSD (≤2GB), microSDHC (4–32GB), microSDXC (64GB–2TB), microSDUC (up to 128TB) | — |
|
Operating Voltages
|
2.7V–3.6V (Standard) / 1.8V (UHS-I signal) | — |
|
Passive Adapter Compatibility
|
Electrically identical to full-size SD (100% pin-compatible via passive sleeve adapter) | — |
|
Speed Class (Legacy C-Class)
|
— | Class 2 (2 MB/s), Class 4 (4 MB/s), Class 6 (6 MB/s), Class 10 (10 MB/s) |
|
UHS Speed Class (U-Class)
|
— | U1 (10 MB/s min sustained write), U3 (30 MB/s min sustained write) |
|
Video Speed Class (V-Class)
|
— | V6 (6 MB/s), V10 (10 MB/s), V30 (30 MB/s), V60 (60 MB/s), V90 (90 MB/s) |
|
App Performance Class A1
|
— | 10 MB/s sequential, Min 1,500 Read IOPS, Min 500 Write IOPS |
|
App Performance Class A2
|
— | 10 MB/s sequential, Min 4,000 Read IOPS, Min 2,000 Write IOPS (requires Command Queue & Host Cache) |
|
Guaranteed Metric
|
— | Minimum sustained sequential write speed on fragmented NAND (never peak burst speed) |