For Secure Digital (SD) memory cards, “digital formats” usually means the card’s capacity standard: SD, SDHC, SDXC or SDUC. These labels tell you the supported capacity range and associated file system—not the card’s physical size or speed. To choose a card, check that your device supports its capacity standard, that its size fits the slot, and that its speed rating suits your workload.
What are the four SD capacity formats?
The SD Association defines four capacity standards. Their stated ranges are standards limits, not a guarantee that every capacity is available to buy or supported by every device.
As an Amazon Associate I earn from qualifying purchases.
| Marking | Capacity range | Associated file system |
|---|---|---|
| SD (also called SDSC, or Standard Capacity) | Up to 2GB | FAT 12/16 |
| SDHC (High Capacity) | More than 2GB through 32GB | FAT32 |
| SDXC (Extended Capacity) | More than 32GB through 2TB | exFAT |
| SDUC (Ultra Capacity) | More than 2TB through 128TB | exFAT |
The 128TB figure is SDUC’s standard upper limit; it does not establish that a card at that capacity is currently available for purchase. The SD Association’s capacity overview lists these ranges and file-system associations: SD, SDHC, SDXC and SDUC capacity standards.
Free tools Windows power users keep installed
One-click scans. No signup required.
Will an SDHC or SDXC card work in an older device?
Compatibility depends on the host device’s supported SD standard. The SD Association’s compatibility table gives this direction of support:
#1 Best Overall
- Save time with card offload speeds of up to 200MB/s powered by SanDisk QuickFlow Technology (Up to 200MB/s read speeds, engineered with proprietary technology to reach speeds beyond UHS-I 104MB/s, require compatible devices capable of reaching such speeds. Based on internal testing; performance may be lower depending upon host device, interface, usage conditions and other factors. 1MB=1,000,000 bytes. X = 150KB/sec. SanDisk QuickFlow Technology is only available for 64GB, 128GB, 256GB, 512GB and 1TB capacities. 1GB=1,000,000,000 bytes. 1TB=1,000,000,000,000 bytes. Actual user storage less.)
- Pair with the SanDisk Professional PRO-READER SD and microSD to achieve maximum speeds (sold separately)
- Shot speeds up to 140MB/s (Write speed up to 140MB/s. Based on internal testing; performance may be lower depending upon host device, interface, usage conditions and other factors. 1MB=1,000,000 bytes. X = 150KB/sec.)
- Perfect for shooting 4K UHD video and sequential burst mode photography (Full HD (1920x1080) and 4K UHD (3840 x 2160) video support may vary based upon host device, file attributes and other factors. See HD page on SanDisk site.)
- UHS Speed Class 3 (U3) and Video Speed Class 30 (V30) (UHS Speed Class 3 designates a performance option designed to support 4K UHD video recording with enabled UHS host devices. UHS Video Speed Class 30 (V30), sustained video capture rate of 30MB/s, designates a performance option designed to support real-time video recording with UHS enabled host devices. See the SD Association’s official website.)
| Host device standard | Card standards accepted |
|---|---|
| SD | SD only |
| SDHC | SD and SDHC |
| SDXC | SD, SDHC and SDXC |
| SDUC | SD, SDHC, SDXC and SDUC |
In other words, support is backward compatible in the direction shown: a newer-standard host accepts older card standards, but an older host should not be assumed to accept a newer one. Check the SD logo and other markings on the device, then confirm the supported card type in the manual or manufacturer’s specifications before buying. The Association’s SD card compatibility information explains the host-and-card relationship.
Are SD and microSD different formats?
SD and microSD refer to physical form factors, not capacity standards. The SD Association lists standard SD dimensions as 32 × 24 × 2.1 mm and microSD dimensions as 11 × 15 × 1.0 mm. An SDHC, SDXC or SDUC card can be made in a physical size that fits a compatible SD or microSD slot; the capacity label alone does not tell you which size it is.
Rank #2
- CAPTURE LARGER THAN LIFE. Unlock 4K UHD(3) brilliance and pristine high res stills with video speed class ratings of U3 and V30(4).
- SPEED BARRIERS SHATTERED. Save precious moments with blazing read speeds up to 250MB/s(2) and write speeds up to 170MB/s(2) [256GB-1TB capacities(1)].
- MAXIMIZE WITH MASSIVE CAPACITY. Capture for longer and store more with up to 2TB(1) of storage that can hold up to 2,808 minutes of 4K UHD video recorded at 30 fps (641MB/minute)(9).
- DEFY THE ELEMENTS. Unrelentingly resilient, Sandisk SD memory cards are engineered to perform in extreme conditions, despite rough handling and constant use.(6)
- CONTENT MANAGEMENT, SIMPLIFIED. Back up, organize, and transfer everything easily with the Sandisk Memory Zone desktop app,(7) whether you use an SD card slot or a card reader.
Make sure the card matches the device’s slot. An appropriate adapter can let a microSD card fit a full-size SD slot, but it does not change the card’s capacity standard or make an incompatible host support it. See the Association’s capacity and card-size overview for the standard dimensions and capacity categories.
Crashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteWindows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallDoes the SD format tell you how fast a card is?
No. SD, SDHC, SDXC and SDUC describe capacity categories. Speed markings and bus-interface labels are separate, and neither should be treated as a promise of a particular real-world transfer rate.
Rank #3
- Save time with card offload speeds of up to 200MB/s powered by SanDisk QuickFlow Technology (Up to 200MB/s read speeds, engineered with proprietary technology to reach speeds beyond UHS-I 104MB/s, require compatible devices capable of reaching such speeds. Based on internal testing; performance may be lower depending upon host device, interface, usage conditions and other factors. 1MB=1,000,000 bytes. X = 150KB/sec. SanDisk QuickFlow Technology is only available for 64GB, 128GB, 256GB, 512GB and 1TB capacities. 1GB=1,000,000,000 bytes. 1TB=1,000,000,000,000 bytes. Actual user storage less.)
- Pair with the SanDisk Professional PRO-READER SD and microSD to achieve maximum speeds (sold separately)
- Shot speeds up to 90MB/s (Write speed up to 90MB/s. Based on internal testing; performance may be lower depending upon host device. 1MB=1,000,000 bytes. X = 150KB/sec.)
- Perfect for shooting 4K UHD video and sequential burst mode photography (Full HD (1920x1080) and 4K UHD (3840 x 2160) video support may vary based upon host device, file attributes and other factors. See HD page on SanDisk site.)
- UHS Speed Class 3 (U3) and Video Speed Class 30 (V30) (UHS Speed Class 3 designates a performance option designed to support 4K UHD video recording with enabled UHS host devices. UHS Video Speed Class 30 (V30), sustained video capture rate of 30MB/s, designates a performance option designed to support real-time video recording with UHS enabled host devices. See the SD Association’s official website.)
Speed-class markings
The SD Association identifies four rating families: Speed Class, UHS Speed Class, Video Speed Class and SD Express Speed Class. These specify minimum sequential card-access performance under defined conditions. The appropriate class depends on the workload, especially when a device needs a sustained minimum write rate. Actual transfer performance varies with the card and device. The Association explains the ratings in its SD speed-class overview.
Bus-interface labels
UHS-I, UHS-II, UHS-III and SD Express identify bus interfaces. The SD Association lists nominal interface speeds of up to 104MB/s for UHS-I, up to 312MB/s half duplex for UHS-II, up to 624MB/s for UHS-III, and up to 3940MB/s for SD Express. These are interface maxima, not guaranteed card speeds. The Association notes that a card’s maximum speed differs from the bus-interface speed and depends on card and device operation. Check both the card and host specifications; see the SD bus-speed overview.
Rank #4
- Fast for better pictures and Full HD video. Full HD (1920x1080) video support may vary based upon host device, file attributes, and other factors
- Great choice for compact to mid-range point-and-shoot cameras
- From 32GB to 256GB(1) to store tons of pictures and even more Full HD video(2). (1)1GB=1,000,000,000 bytes Actual user storage less
- Exceptional video recording performance with UHS Speed Class 1 (U1)(5) and Class 10 rating for Full HD video (1080p)(2). (5)UHS Speed Class 1 (U1) designates a performance option to support real time video recording with UHS enabled host devices
- Quick transfer speeds up to 100MB/s. Up to 100MB/s[64GB-256GB; 90MB/s for 32GB] read speed; write speed lower Based on internal testing; performance may be lower depending on host device, usage conditions, and other factors 1MB=1,000,000 bytes
How to choose the right SD card standard
- Check host compatibility. Look up the device’s supported SD standard in its manual or manufacturer information; do not infer support from the slot’s appearance alone.
- Match the physical size. Choose standard SD or microSD to suit the slot, or use an appropriate adapter where supported.
- Choose capacity within the supported standard. A host that supports SDXC, for example, accepts SD, SDHC and SDXC under the Association’s compatibility table, but not SDUC unless it is listed as SDUC-compatible.
- Match performance to the task. Select a relevant minimum speed class for the workload and confirm that the host supports the card’s bus interface. A higher interface maximum by itself does not guarantee faster performance in a particular device.
The SD Association describes SD cards as removable memory used across many device categories, but that broad use does not make standards universally interchangeable. Device-specific support remains the deciding factor.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Quick Recap
Best Value
- Great choice for compact to mid-range point-and-shoot cameras
- Quick transfer speeds up to 140MB/s (Up to 140MB/s read speed engineered with proprietary technology to reach speeds beyond UHS-I 104MB/s, requires compatible devices capable of reaching such speeds. Based on internal testing; performance may be lower depending on host device, interface, usage conditions and other factors. 1MB=1,000,000 bytes.)
- Up to 128GB to store tons of pictures (1GB=1,000,000,000 bytes. Actual user storage less.)
- Exceptional video recording performance with UHS Speed Class 1 (U1) Class 10 rating for Full HD video (1080p) (UHS Speed Class 1 (U1) designates a performance option designed to support real time video recording with UHS enabled host devices. See consumers speed page on SanDisk site. Full HD (1920x1080) video support may vary based upon host device, file attributes, and other factors. Visit the SanDisk Video Knowledge Base for more information.)
- Compatible with SanDisk SD UHS-I card reader (sold separately)
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
