TBF-RnD is an open source project that currently focuses on input mechanisms. For an introduction on why this might be interesting to you, check out this post. We’re doing experiments like a prototype for an easy to learn chorded input mechanism.

A small “Plain Old Keyboard”

Early work by Troy Fletcher

Obviously a lot of clever people have thought about how to make keyboards better. One of the most obvious candidates for attributes that can be optimized on an input device is naturally its size. Above you’ll find a 40% keyboard.

Note that the keymap doesn’t have the row of numbers that you’ll probably find on your keyboard. Also there are no arrow keys. At first glance, it seems that this would only harm productivity, and still some people swear by it.

VIM-style movement and Fitt’s law

Vim users will be familiar with the concept of using the keys h,j,k & l for navigation instead of using the arrow keys. This is a historical artifact and may not be due to speed related reasons. Still a lot of programmers swear by using these keys for navigation. Why is this? Well, by having the navigation keys closer to the home row, you don’t have to move your hands as much.

Reducing unnecessary movement is something that is of a great interest for me. I’m particularly interested in finding out how well a setup using a “FPS-stance” would fare, i.e. typing only with the left hand and using the mouse for secondary actions. You can read more on that in this post.

Fitt’s law: the time required to rapidly move to a target area is a function of the ratio between the distance to the target and the width of the target.

It’s sort of obvious to figure out that the less we have to move our hand from the home row to the arrow keys, the more time we save. There is however a more formalized way to look at this in the field of user interface design.

With a 40% keyboard, we have to move the fingers less as well. No more than one key has to be travelled to find any other key. Fitt’s law states that if we have to move the finger, the size of what is to be hit has to be increased, or we’ll suffer an increased error rate.

Programmable keyboard for further functions

Creating your own keyboard from a kit and using an open source firmware buys you a lot when it comes to customizability. For example, you can have different functions on the same key depending on how you press it. The same key could be used for Escape and Ctrl for example.

R.S.I Repetitive Strain Injury

Split keyboard design by Troy Fletcher

One of the advantages with a small keyboard layout is that if you only have to move the fingers, you can keep your wrists in static positions. This would at least in theory be advantageous for people suffering or who are at risk for R.S.I.

Split keyboard layout designs have been used to mitigate these effects. The split design is more easy on the wrist and conforms to a more natural way of placing your hands.

How does it work?

So a 40% doesn’t have very many keys – how can it possibly be usable? Well the answer is the following: By using layers activated by modifiers, similar to how shift, alt or function keys work, the missing keys are added. Theoretically this is sort of adding an extra component to the input, so it can be thought of as a subset of chorded typing. Only adding one key however makes it easier to figure out which keys are to be interpreted as a single input signal.

Example keymap for a 40% layout

Get in touch and get updates

If you are interested in this blog please enter your contact details above and we can get in touch with you. Maybe you have some ideas of your own, feel like helping out with code or maybe just have a chat with cool people!


Whereas a computer programmer might see benefits from using a 40%-keyboard and an enthusiast might get hours of fun out of tinkering with the electronics, I do not believe that it’ll reach mainstream adaptation. Still I find that we can draw interesting conclusions from the concept.

First of all, the reduced distances will increase speed, something that becomes especially interesting if we go even further and reduce the numbers to – say – 10 keys. This means that for example, a gamepad configured to use a clever scheme, could tap into higher typing speeds by totally eliminating finger movement between buttons.

If it turns out that 40% keyboards can reduce Repetitive Strain Injury or R.S.I. we can try to construct the input methods of the future with these lessons in mind.

Support the effort

All of this is done on an ideal open source basis. To keep it that way your support is very needed. Please get in touch if you have ideas, share with people that might and check out patreon below!

References and further reading

The images in this post is of the designs of Troy Fletcher, who reached out to me earlier. I’ve discussed the matter with him and his web site is a great source of information on the subject. A brilliant man with a great deal of passion who also has a lot of insights into other things. If you also have ideas on this subject or believe that I am totally wrong, don’t hesitate to write a comment below or fill in our contact form!

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