When looking for an SD card, one of the most important factors to consider is the potential maximum storage capacity. SD cards come in different formats that support different maximum capacities. Choosing the format with the highest capacity ensures you can store more photos, videos, music and other files on a single card.
SD, SDHC and SDXC Formats
There are three main formats for SD cards – SD, SDHC and SDXC. Each format has its own limitations on maximum capacity:
- SD – up to 2GB
- SDHC – up to 32GB
- SDXC – up to 2TB
So clearly, SDXC has the potential for much higher capacities than the other two formats. The SDXC specification was introduced in 2009 to allow cards with capacities larger than 32GB. While 2TB is the current maximum capacity, the SDXC format is designed to support cards up to 128TB once technology allows it.
Why SDXC Supports Higher Capacities
The reason SDXC cards can reach 2TB and potentially 128TB in the future comes down to how they address memory. The original SD format used FAT32 file formatting, which limited capacities to 32GB. SDHC switched to the exFAT file system which increased the limit to 32GB.
SDXC uses a different file system again, known as UFS2. This allows the use of much higher capacities. So the SDXC card format builds on its predecessors by utilizing newer file formatting technologies as they become available.
Real-World SDXC Cards
While SDXC theoretically supports up to 2TB, most consumer SDXC cards currently on the market top out at 1TB. However, there are a few 2TB options available. Here are some examples of high-capacity SDXC cards:
| Manufacturer | Model | Capacity |
|---|---|---|
| SanDisk | Extreme PRO SDXC | 1TB |
| Lexar | Professional 2000x SDXC | 1TB |
| Samsung | EVO Select SDXC | 1TB |
| Kingston | Canvas Select Plus SDXC | 2TB |
As you can see, 1TB cards are reasonably widely available from major brands. The 2TB Kingston card shows that SDXC capacities are continuing to grow.
Speed Considerations
One downside of the highest capacity SDXC cards is that they generally have lower speed ratings than smaller cards. This is because writing to and reading from large NAND flash memory chips tends to be slower at present. So the 2TB Kingston Canvas Select Plus card only claims read speeds of 100MB/s, compared to 300MB/s for a top-end 128GB card.
If you need both large capacity and top speeds, you may want to consider other formats like CompactFlash or CFast 2.0. These leverage technology like RAID configurations to deliver both high speeds and large capacities. However they are larger and more expensive than SD cards.
Conclusions
To summarize the key points:
- SDXC is the SD card format with the highest maximum capacities, theoretically up to 2TB
- It uses advanced file formatting (UFS2) to support large capacities beyond 32GB
- 1TB SDXC cards are available today, with a handful of 2TB options as well
- The highest capacity cards tend to have lower speeds than smaller SDXC cards
- Other formats like CompactFlash can combine high capacity and speed
So if you purely need the largest possible capacity in the convenient SD format, SDXC is the clear choice. Just be aware that you may have to sacrifice some speed compared to smaller SD cards. As NAND flash technology progresses, we should see SDXC cards continue to grow in capacity while hopefully also increasing their speed ratings.
Frequently Asked Questions
What’s the difference between SD, SDHC and SDXC cards?
The main difference is the maximum capacity each format supports:
- SD – up to 2GB
- SDHC – up to 32GB
- SDXC – up to 2TB
SDXC uses more modern file formatting (UFS2) to support capacities above 32GB.
How much higher can SDXC capacities go?
The SDXC specification theoretically supports up to 128TB. However capacities are limited by current NAND flash technology. We can expect capacities to steadily increase as technology improves, but it will likely be many years before we see 128TB SDXC cards.
Are there any downsides to high capacity SDXC cards?
The main downside is slower speed ratings compared to smaller SD cards. For example, a 1TB card may have read speeds around 100MB/s, while a 64GB SDXC card can easily exceed 300MB/s. This is because NAND performance tends to decrease at higher densities. If you need both high capacity and speed, other formats like CompactFlash may be preferable.
Which brand makes the fastest high capacity SDXC cards?
Major brands like SanDisk, Lexar and Samsung all make high performance SDXC cards with 1TB capacities. However, exact speed ratings vary between models. Lexar’s Professional 1667x 1TB card can reach maximum read speeds of 250MB/s, making it one of the fastest options available. But you’ll pay a premium for these top speeds at such high capacities.
Are there any 4K or 8K rated ultra high speed SDXC cards?
Yes, some companies like Sony and Kingston now offer SDXC cards with rated video speeds fast enough for 4K and 8K recording. For example, Sony’s SF-G series includes a 256GB card rated at 299MB/s write speed, which qualifies as ultra high speed. Again though, these very fast cards are not yet available in the highest 1-2TB sizes.
As SDXC cards continue to grow in capacity, we can expect more models to meet the ultra high speed classification for 4K/8K video in the future. But for now, you generally have to choose between maximum capacity and maximum speed when choosing high performance SDXC cards.
Comparison of File Systems
When choosing an SD card, it’s important to understand the file system. This determines the maximum possible capacity and performance characteristics. Here’s an overview of the primary file systems used by SD cards:
| File System | Maximum Capacity | Speed/Performance |
|---|---|---|
| FAT32 | 32GB | Good overall performance |
| exFAT | 256TB theoretically | Faster than FAT32 for large files |
| UFS | Up to 2TB currently, 128TB theoretically | Optimized for high-capacity cards |
As you can see, UFS used in SDXC cards allows for much higher maximum capacities. However, exFAT offers a balance of large capacity with faster performance. This makes exFAT a popular choice for large external USB drives.
Tips for Choosing an SD Card
Here are some tips when shopping for the right SD card for your needs:
- Consider your storage needs – do you need a large capacity card for lots of HD video?
- Check card read/write speeds – make sure it’s fast enough for your camera or device
- Choose a reputable brand for reliability
- Compare prices between retailers to find the best deal
- Look for deals on card reader bundles for easier file transfer
- Check warranty and support options in case you need to replace the card
Getting the right combination of price, capacity, speed and reliability requires some research. But taking the time to choose the right SD card will ensure you can safely store all your photos, videos and other data.
SD Card Storage Limits Based on Format
Below are the theoretical maximum storage capacities for different SD card formats and types:
| Format | Maximum capacity |
|---|---|
| SD | 2GB |
| SDHC | 32GB |
| SDXC | 2TB |
| SDIO | No defined limit |
| miniSD | 2GB |
| miniSDHC | 32GB |
| microSD | 2GB |
| microSDHC | 32GB |
| microSDXC | 2TB |
As you can see, the SDXC format provides the highest potential capacity by far. Extended capacity SDXC cards will continue pushing this limit as NAND flash technology evolves. The SDIO format used in integrated SD card applications does not specify a maximum.
Choosing Between SDHC and SDXC
Both SDHC and SDXC allow for significant storage capacity well beyond the 2GB limit of standard SD cards. So which should you choose? Here are a few key differences:
- Maximum capacity – SDHC supports up to 32GB while SDXC can reach 2TB.
- Speed – SDHC has slower maximum speeds of 104 MB/s compared to 312 MB/s for SDXC.
- Device compatibility – Some older devices may not recognize SDXC cards.
- Price – SDHC tends to be cheaper at capacities below 32GB.
For most users, SDHC offers a good balance of improved capacity beyond standard SD, while maintaining wide device compatibility. Power users needing huge capacity for 4K video and other data should look to SDXC. SDXC is also better future-proofed to take advantage of capacity increases.
SDXC UHS Speed Classes
SDXC cards also support Ultra High Speed (UHS) ratings for improved performance. There are three UHS speed classes:
- UHS Speed Class 1 – Minimum 10MB/s write speed
- UHS Speed Class 3 – Minimum 30MB/s write speed
- UHS Speed Class 1 – Minimum 60MB/s write speed
Cards with UHS ratings are optimized for high-bandwidth applications like burst shooting photos or 4K video capture. Look for cards carrying the U, U3 or U1 rating if you need maximum SDXC performance.
SD Express – Future SD Card Format
A new SD card format called SD Express offers further enhancements in speed and capacity potential. It combines the SD interface with the PCI Express and NVMe interfaces used in solid state drives. Here are some key enhancements with SD Express:
- Up to 985MB/s data transfer speeds
- Leverages PCIe Gen 3×1 or Gen 3×2 interfaces
- NVMe protocol optimized for flash memory
- Backward compatible with existing SD interfaces
- Supports SDMB standard for managing memory
SD Express will help SD cards continue evolving to support new devices with even greater speed and resolution requirements. The first SD Express cards should hit the market in 2020, focused on high-end use cases.
How SD Express Improves Speeds
SD Express achieves much faster speeds than traditional SD cards by using the PCI Express and NVMe interfaces commonly found in solid state drives:
- PCI Express – Serial connection replaces SD parallel bus, increasing theoretical limit from 104MB/s to 985MB/s.
- NVMe – Optimizes communication between SSD controller and flash memory for lower latency.
By combining these advanced interfaces with the reliable SD form factor, SD Express will help high-speed cards keep pace with rising resolution of media and devices.
Conclusion
In summary, SDXC currently offers vastly higher potential storage capacities compared to SD and SDHC, due to the advanced UFS file system. Real-world SDXC cards are available up to 1TB today, with some pushing capacity limits up to 2TB. However, there are some tradeoffs – the highest capacity cards tend to have lower speed ratings than smaller cards.
Looking forward, the SD Express format will help increase speeds dramatically using PCIe and NVMe interfaces. SD cards continue to evolve both in capacity and speed to meet the needs of the latest cameras, smartphones and other devices. Carefully considering your own speed and capacity requirements will help you choose the right SD card format and model for your needs and budget.