A Framework to Determine Which Keycaps Fit Your Mechanical Keyboard
Whether you bought a custom keyboard or a pre-built one, one of the things you can easily customize are the keycaps.
The problem is, with all the keyboard layouts and designs, the number of choices can be daunting and people new to the hobby inevitably ask: how do I know whether a keycap set fits my keyboard?
While you can ask an expert for a definite answer for each keyboard configuration, it’s much more valuable to give people a framework so that they can determine it for themselves. This is important as some manufacturers have different implementations of popular layouts so identifying these exceptions can save you time and money.
What to Look For
In general, there are three questions you need to answer to determine whether a keycap set fits your keyboard:
1) Is it Cherry MX compatible?
2) What keycap profile does it use?
3) What sizes are the keycaps?
Is it Cherry MX compatible?
Most — but not all — of the keycaps on the market are Cherry MX keycaps, which means most of what’s available will fit Cherry MX-style switches. This doesn’t mean your switches need to be Cherry-branded. Manufacturers like Kailh, Gateron, Outemu, etc., use Cherry MX-style switches, and this can be seen by the “+” looking stems of the switches (or the bottom of the keycaps).
Other types of switches on the market include Alps, Topres, Choc, and low-profile switches, so as long as you avoid these switches, your Cherry MX keycaps will probably fit. And if you happen to have a keyboard that has these switches, then you should be aware that your keycap options are more limited.
What keycap profile does it use?
The term “profile” can mean many things in keyboard jargon, so as to not confuse people, let me describe the three instances it’s used, and how it may affect your keycap choices.
High Profile vs Low Profile Keyboards
The first instance is when it’s used to describe the height of the keyboard in relation to the keyboard case and its switches. High profile keyboards are constructed so that the bottom of your switches aren’t visible. Low profile keyboards are the opposite and you can see the bottom of the switches even with keycaps on them. This has no bearing on whether Cherry MX keycaps are compatible with your keyboard.
One example of this is the Drop Alt and the Drop Alt High Profile:
Low Profile Switches
Some keyboards, to reduce the overall height, use low-profile switches and low-profile keycaps. It doesn’t make sense to have a short switch only to have a tall keycap for example. Unfortunately, this also means a lot of keycaps for low-profile switches have to be specifically designed for the switch they’re going to be used, which in the first place isn’t standarized. (Keychron, with the release of its low-profile optical switches when it launched the K3, is attempting to create a new standard, but that attempt is moot if others don’t end up using your standard; Keychron’s low-profile optical switches are mostly compatible with Cherry MX keycaps, but what’s the point of pairing a short switch with a tall keycap?) If you happen to own a keyboard that uses low-profile switches, don’t expect to easily find replacement keycaps not from the manufacturer.
Keycap Profiles
This is one of the important things to recognize when browsing keycaps. Keycaps come in different profiles — or rather, they implement different standards. The most popular by far are Cherry profile and OEM profile, but you can expect to see other profiles in the market such as DSA or MT3.
Keyboard University has a more detailed breakdown of the various profiles, but what’s important to know is whether the keycap profile is sculpted (i.e. different rows have different heights) or uniform (i.e. all of the keycaps have the same height).
Here’s an example. Let’s say you want to swap the positions of letters “A” and “Q”. With uniform profile keycaps, it won’t really be an issue. With sculpted profile keycaps, it is visibly apparent that “A” and “Q” do not belong in the right row as the “A” might be shorter compared to the keycaps beside it while “Q” will be slightly taller.
Another thing to note is that the R3 of Cherry profile keycaps, when used with north-facing switches, can cause “interference”. Interference is described as a difference in sound and feel. Depending on who you are, this interference might be negligible or noticeable. Some switches, such as Glorious Pandas and Kailh Box Creams, do not suffer from interference regardless of orientation.
What sizes are the keycaps?
Once you’ve identified the keycap profile, we can get into the nitty gritty of keycap sizes.
First, the unit of measurement used in keycaps is u, or 1u in the case of a regular-sized keycap. A keycap that’s twice as long would have 2u for example. (And keycaps that are 2u or longer require stabilizers.)
Second, you need to know the keycap size that your keyboard uses. If you’re using a full-sized keyboard or a tenkeyless keyboard, you’ll probably be fine with most sets, as they comply with most 104-key sets. It’s when you go smaller that it becomes tricky.
Perhaps the easiest way to understand keycap sizes is to look at a full-sized keyboard, use it as reference, and then compare it to the keycaps required by a smaller keyboard.
Here’s one layout that I find useful from Keychron, as it shows the sizes of keycaps in a standard keyboard and labels them accordingly.
The next step is to look at the layout of the keyboard you’re interested in.
With practice, you can eyeball the sizes you need, but for now, let’s rely on a visual guide. Let’s say you’re looking to purchase the GMMK Pro but don’t know what its keycap sizes are.
A similar-looking keyboard is the Keychron K2 and its keycap sizes can be found here.
The first thing you want to do is compare the two and determine which keycap sizes are different. If there’s none, then you’re good to go with the basic 104-key set.
In this example though, that’s not the case. The first major difference is the right Shift key. It’s normally a 2.75u keycap but in this case, it’s a 1.75u keycap. That’s the first keycap size we should be looking for.
To put that into practice, look at this PBT Miami Set from Tai-hao. It only has 104 keys, so it would fit a full-sized keyboard, but not the GMMK Pro or K2, because it’s lacking a 1.75u shift. Luckily, Tai-hao also sells a 1.75u shift separately, so that can be an option.
Looking back at the layout, that’s not the only keys that are missing. The right modifiers — the keys to the right of the space bar — are also different. They’re normally 1.25u but in this case, they’re 1u.
You can theoretically just swap them out with a different 1u key, but remember our discussion about Profiles? If we insert the keycaps from a different row, their height might appear different if you’re using a sculpted profile, which may or may not be a dealbreaker for you.
Let’s take a look at this ABS-Cubic Profile 128 KEYS WoB from Tai-hao. It has more keys than the usual, but the question is whether it will have the keys you need.
If you look at the second to the last row (R1), it shows that it has a 1.75u shift, so that part is covered.
But what about the right modifier keys? In this case, it’s R0, and if you look at the bottom row (R0), there’s four blank 1u keycaps that you can use to take the place of the right modifier keys.
Here’s a caveat. For the GMMK Pro and the K2, it has keycaps like Page Up, Page Down, Home, and End. However, they’re arranged differently compared to the full-sized keyboard, and whereas previously they occupied R4 and R3, they now occupy R4 until R1, depending on how you arrange them. What happens if you place them in R1 and R2? Well, their height might look different compared to the other keys if we’re using a keycap set with a sculpted profile (which is the case with the Tai-hao keys as they’re OEM), but that’s one thing to keep in mind.
Layouts Aren’t Standarized
While we’ve provided a basic framework, you also shouldn’t rely on keyboard size to determine whether keycaps will be compatible with your keyboard.
There’s a lot of change and innovation that’s happening in the custom keyboard space, but this also means that elements aren’t standarized.
Take for example the following 65% entry-level custom keyboards. They all qualify as 65%, but the keycaps required for them vary.
Ikki68 Aurora
A regular shift fits the Ikki68 Aurora, so a regular keycap set would fit. Same goes for the placement of Page Up/Page Down/Home/End keys. The tradeoff here is that while this is a 65% keyboard, it’s longer than most 65% and is only a column shorter than most tenkeyless keyboards.
KBD67 Lite
The KBD67 Lite requires a 1.75 right shift. Other than that, there’s the usual caveats for the Page Up/Page Down/Home/End keys, as some of these would fall to R1 and R2.
NK65 Entry Edition
In addition to the 1.75u right shift, the NK65 chooses to use 1u right modifier keys. This means there’s one more modifier key compared to the KBD67 Lite, but you’ll need to find specific keycaps for these.
Conclusion
While it would be useful for manufacturers to provide users with keycap sizes for their keyboards — in much the same way Keychron does with their keyboards — unfortunately that’s not how they market their products.
The good news is that with practice, you’ll eventually be able to identify sizes of different keycaps at a glance, and this will eventually become second nature. The bad news is that this takes practice and time — and maybe even making some errors from time to time.
