How to Tell UHS-I and UHS-II Cards Apart

If you’ve looked at buying an SD or microSD card, you might have run into codes like UHS-I and UHS-II on the label.

It refers to something called ultra high-speed bus, which in turn refers to the interface between the card and the device. So far, there is UHS-I and UHS-II. UHS-I caps out at 104MB/s; UHS-II raises that ceiling to 312MB/s. Those are theoretical maximums for the bus rather than speeds you’ll see in real shooting, but they’re the reason a UHS-II card can be so much faster when the device can actually use it. There is a specification of UHS-III, but I’ve not seen any cards actually turn up using that yet — that standard was effectively passed over in favor of SD Express.

UHS-II is the newer, and potentially faster, system. It’s standard on enthusiast and pro cameras now, but plenty of cameras, phones, and card readers are still UHS-I only. And a UHS-II isn’t necessarily guaranteed to be faster than every UHS-I card in practice. While it wasn’t always true initially, the current fastest SD cards are UHS-II (when used with a UHS-II compatible host, that is).

Related: not sure how much of this speed your camera can actually use? See What Memory Card Speed Does Your Camera Actually Need?

Compatibility

The UHS-I and UHS-II specifications are designed to be backward compatible. That means that you can use a UHS-II card in a device that’s compatible with UHS-I and vice versa. But if you do so, you’ll be limited to the lower spec, in this case UHS-I. That is the general intention, at least. But it gets a little more complicated, because there are different implementations of UHS-I that have different speeds. Some cards fall back to a slower UHS-I spec; better cards fall back gracefully to a UHS-I spec known as SDR104. Unfortunately, that particular part of the card’s capabilities is rarely specified in either the packaging or the technical specs.

But in many cases, it frankly doesn’t matter which you get. But that’s simply because a lot of cameras, phones, and readers still use a UHS-I interface, and in those you’ll get UHS-I speeds no matter which card you put in.

And some that are UHS-II compatible can be a bit quirky. For instance, the Fujifilm X-Pro 2 camera has two SD slots. But only one uses UHS-II. So if you put a UHS-II SD card in the slot that has the UHS-I interface, you’ll be limited to UHS-I speeds.

But if you have a device that does use the UHS-II interface — and the technical specs or instruction manual will say so if it does — then there’s a good chance you’ll get better performance out of a UHS-II card.

The microSD side deserves a separate mention, because UHS-II microSD cards exist but very few devices can use them. Phones, action cameras, and drones are essentially all UHS-I: GoPro’s card slots run on a UHS-I bus, and even a current camera like the Ricoh GR IV lists its microSD slot as UHS-I only. A UHS-II microSD card will still work in those devices, but you’d be paying for a bus they can’t touch.

One common device where this can become an issue is with memory card readers. Plenty of cheap readers are UHS-I only, and so are many of the card slots built into laptops. UHS-II cards will work in them, but they’ll be limited to UHS-I speeds. Dedicated UHS-II readers are much easier to find now than they used to be, such as the SanDisk Extreme Pro reader, but you still can’t assume that every card reader supports UHS-II.

How to tell if a card or camera is UHS-I or UHS-II

There are two ways to tell the difference. The first is obvious: look at the label or packaging. They’ll have either UHS-I or UHS-II, or sometimes just I or II. Technically, it should be Roman numerals, but you’ll sometimes see it incorrectly written as a number 1, like UHS-1.

You can also tell them apart by looking at the cards themselves. UHS-I cards have a single row of pins on the back. UHS-II cards have two rows. In this example, both of these are SanDisk Extreme Pro cards, just different generations.

Working out whether your camera can use UHS-II is a matter of checking its specs, not the camera itself — cameras don’t report which bus mode they’re running. The memory card line in the specifications or the manual will say UHS-II if the slot supports it; if it only lists SD/SDHC/SDXC or UHS-I, that’s what you’ve got. On bodies with two slots, check both, because it’s common for only one of them to be UHS-II. And the bus is hardware, so no firmware update or menu setting will turn a UHS-I slot into a UHS-II one.

U1 vs U3 vs V30 vs V60 vs V90

The UHS-II code isn’t the only new code you’ll see on some microSD and SD cards. There’s also a new code that relates to suitability for recording high-resolution video. U1 and U3 have been around for a while. The V ratings came later: V30, V60, and V90 guarantee minimum sustained write speeds of 30MB/s, 60MB/s, and 90MB/s. There’s one useful link back to the UHS side — a UHS-I card can be rated up to V30, but only UHS-II cards can be certified V60 or V90. So if a camera asks for a V60 or V90 card, it’s asking for a UHS-II card.

All of these are speed classes aimed at recording high-resolution video. And they’re a separate designation from the UHS-I vs UHS-II one. I have more detail on the V30, V60, V90, U3, and Class 10 speed classes here.

Memory card tools

Here are a few other related tools I’ve put together that can be useful when working with memory cards and data rates.

Converting Mbps to MB/s & X speed rating to MB/s

Another related and common calculation that often needs to be done when working with memory cards is converting the convention for measuring video bitrate (Mbps, Mb/s, or megabits per second) to the convention for measuring the speed of memory cards (MBps, MB/s, or megabytes per second).

So I’ve put together a simple calculator for that separately. You can find it here:

• Convert Megabits Per Second to Megabytes Per Second Calculator
• Convert Memory Card X Speed Rating to MB/s

Memory card size calculators

If you’re trying to figure out what size memory card to buy, it can be useful to know how much video footage from the camera you can fit on a card. Here are a few tools that can be useful for that:

• Video Bitrate vs Memory Card Size Calculator
• How Much 4K Video Can 128GB Hold?
• How Much 4K Video Can 256GB Hold?
• How Much 4K Video Can 64GB Hold?

Working with memory cards

Here are some related posts for making sense of memory cards and working with them.

• Fastest SD Card Speed Tests. With cameras getting improved 4K, 5K, and even 8K video recording and burst shooting features all the time, some of them need the write speeds that only the fastest SD cards provide. So here’s a roundup of the fastest SD cards based on my independent tests.
• Fastest MicroSD Card Speed Tests. Need a fast microSD card? If you’re shooting 4K, 5K, or 8K video, high-speed burst-mode photos, or some other demanding use, speed matters. These are the results from my independent speed tests of the fastest microSD cards.
• Types of SD Cards Explained. There are several different types of SD cards, as well as multiple speed rating systems and cryptic codes. Here’s a rundown of what the differences are.
• UHS-I vs UHS-II on microSD & SD Cards. Wondering what the difference is between UHS-I and UHS-II with SD and microSD cards? Here’s an explanation.
• A1 vs A2 SD cards and microSD Cards You might have seen new A1 and A2 speed ratings on some of the newer SD and microSD cards. So what do they mean? And when should you take notice of it?
• SD Card Formatter App for Formatting, Wiping & Repairing SD & microSD Cards. Here’s a guide to using the SD Association’s official SD Card Formatter for preparing your SD and microSD cards for use.
• How to Format SD Cards on Mac. Here’s a step-by-step guide for formatting both SD and microSD cards.
• Best Free Data Recovery Software for SD Cards. Here’s a rundown of the best free data recovery software to use if you’ve accidentally deleted photos or videos from your SD card.
• How to Rover Deleted Photos from SD Card: SD Card Recovery Options. All those photos you took have disappeared from the SD card. The good news is that there’s still a good chance you can recover photos from the SD card. Here’s what to do. Includes free and paid SD card recovery options.