Your friend challenges you to a mano-a-mano typing face-off on typeracer. Giving in to your hubris, you gladly agree. She clocks in at 70 words per minute but you barely manage an embarrassing 56 words per minute. What do you think went wrong? If your first instinct was to blame the keyboard, turns out you aren’t being as big a cry baby as you’d think. Aside from your innate skill, key spacing on a keyboard does indeed affect your typing speed. For regular users indulging in casual gaming and keyboard warfare on social media, the effects wouldn’t matter much. It matters when you’re designing keyboards for people who spend half of their day smashing their fingers on them for actual work – so basically writers like yours truly.
There are several factors that affect your typing speed such as key spacing, travel distance, actuation distance, type of switch, etc. In this article, we’ll be exploring a study on how key spacing impacts typing speed, errors, and usability.
What is key spacing?
Key spacing is the distance between the midpoints of two keys, both horizontal and vertical. Normally, key spacing on modern keyboards has always been around 3/4 of an inch or about 19 mm (+\- 1 mm). Regular keys such as alphabets, numbers, symbols, etc., also known as Alpha keys, are usually 18 mm wide. Alpha key widths are also denoted as 1X or 1µ so that it’s easier to mention the sizes of other keys as a multiplier. Ctrl, Alt, and Windows keys have either a width of 1X1.5 or 1X1.25, depending on the manufacturer. Tab and Backslash are 1X1.5, Caps Lock is 1X1.75, and Backspace is 1X2. The Left Shift key is 1X2.25 and the Right Shift Key is 1X2.75, whereas the Enter or Return key has a width of 1X2.25. The width of the Enter key also depends on the layout, whether it’s ISO (American) or ANSI (European). The width of the Spacebar can either be 1X6.25 or 1X6.5, again dependent on the manufacturer.
There have been few studies before exploring the optimal key spacing distance. A 1972 literature review, mentioned key spacing as something determined by “design conventions” and not on “empirical data”, where the spacing was typically 18.1 mm. Another study from 1987 recorded performance, percentage error, and user preference. This study revealed the sweet spot to be 19 mm in horizontal and vertical spacing but again, it was riddled with problems. There were two other studies as well which again pointed towards the now adopted key spacing of 19 mm.
A new study appears
A team of researchers conducted a study on “The Effect of Keyboard Key Spacing on Typing Speed, Error, Usability, and Biomechanics” back in 2012. The objective of this study was to determine the effects of key spacing on typing speed, percentage error, usability, and forearm muscle activity and wrist posture. It overcame the shortcomings of the older studies by considering physiological factors of subjects, essentially, adding a parameter for smaller and larger fingers. The study was conducted in two parts, where the first part looked into horizontal spacing while the second explored vertical spacing.
The study methodology
The team from the School of Public Health at the University of California at Berkeley, evaluated part one of the study on 37 male typists between the age of 18 and 65 who had a minimum capability to type 30 words per minute. The mean middle finger length (lol we know) of the candidates was 8.7cm or more and the finger breadth was 2.3cm or more. The second part consisted of 26 female participants with small fingers and male participants of the same number with larger fingers. For the keyboard, an Ergodex DX1 with a QWERTY layout was employed in five different configurations in terms of key spacing. These included four keyboards with a horizontal spacing of 19, 18, 17 and 16 mm and all of them had 19 mm in vertical spacing. The fifth keyboard had horizontal and vertical spacing of 17 mm. There were several more intricate parameters kept standard across the candidates. These studies intended to cover variables that included typing speed, percentage of error, subjective ratings and rankings of usability and fatigue, keyboard preference by users, left and right wrist ulnar deviation posture, and forearm muscle activity.
The results weren’t shocking
You might be wondering that adding a few parameters to the new study should have drastically affected the results and given us a surprising result. Nothing of that sort happened and the conclusions were already expected. From part one of the study, the typing speed, error and usability ratings among candidates with large fingers were the same for horizontal key spacing between 17 and 19 mm. However, when the keys were further crunched up together, i.e. when they were 16 mm apart, errors started increasing typing speed slowed and usability ratings dropped. They also observed that these parameters didn’t change much when the vertical spacing was 17 or 19 mm. This means that if you have large fingers, you will definitely be able to comfortably and efficiently type with a horizontal spacing between 17 and 19 mm, but anything lower will affect your typing. In part two, it was found that the above parameters remained the same for vertical key spacing between 16 and 18 mm for both males and females with larger and smaller fingers, respectively. The measures were significantly poor when the spacing was 15.5 mm. So, vertical spacing is agnostic of whether you have larger or smaller fingers when it’s between 16 and 18 mm, but it does affect both when the spacing is 15.5 mm.
Until now, the 19 x 19 mm horizontal and vertical spacing was used as a standard based on older research addressed in the study. But it turns out the standard spacing does come out to be the best from the first part of the study itself. The difference this time is that we have more variables to ensure the claim. For a far more detailed study, it would be interesting to find out how the different layouts including QWERTY, DVORAK, COLEMAK, etc., would affect the results. We all know how the QWERTY layout was dictated by the erstwhile typewriters because of mechanical limitations. We are pretty sure that the newer and efficient layouts will yield better productivity results.
A third part was also researched that covered the effect of key gaps, which is the distance between the edges of the keys. You can read the study here. The same parameters from part one and two were considered and it was found that a gap of 5 mm gave better accuracy, typing speed and usability measures.
Although this research doesn’t really matter to regular users of keyboards, it’s a great thing to know that the key spacing on your physical keyboard has been justified with an exhaustive research. If you’re a keyboard geek and wish to get your hands dirty with building your own keyboard, these numbers will surely help you when you’re designing the PCB of the keyboard. This data means a lot to keyboard manufacturers whether for desktop or laptops. Since there wasn’t much difference in typing efficiency horizontal and vertical spacing between 16 to 19 mm, manufacturers can shrink the size when it comes to designing small form-factor keyboards. Having a standard is vital when it comes to typing and data entry as employers wouldn’t want to alienate them with different sizes and layouts after replacement of older or damaged hardware.