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Keystroke Level Model Calculator

About the Keystroke Level Model

Card, Moran and Newell proposed a keystroke-level model that predicted the efficiency of an interface for an expert user.

For most systems, there are 5 components:

  • K (0.2 s) – press a key or mouse button
  • P (1.1 s) – point with mouse
  • H (0.4 s) – home on keyboard, mouse or other device
  • M (1.35 s) – mentally prepare
  • R (t) – system response time (needs to be measured)

There are some rules for how these times are applied (simplified): M should go in front (or between) all operations unless they are fully anticipated. H is inserted each time a user moves between devices (from keyboard to mouse, for example). A much more detailed description can be found in their book, The Psychology of Human-Computer Interaction (click here for

The free Windows-based KLM calculator simply adds up the appropriate times for any string of actions entered. So, for example, getting to the Insert->Break dialog in Microsoft Windows while in the middle of typing looks like this in KLM terms:


That is a mental preparation, followed by a 'home' (movement from keyboard to mouse), followed by two pairs of points and clicks on the mouse.

Just type this string (in upper or lower case and with any punctuation you might fancy) and the result appears as shown below:

Image of KlmCalc window showing actions and calcuated result

The Clear button lets you start again from scratch. That is all there is to it. If you want to find out what time values are being used for each action, just enter those actions individually.

You can download the application below. It should run on most versions of Windows. (Sorry Mac users - I asked Apple in 1984 what I would need to develop software for their new machine and they told me I would have to buy a Lisa, but they really did not want other people writing software for it. I haven't got around to seeing what the price of a Lisa is these days.)

Free KlmCalc Download

Right-click to download KlmCalc V1.0 for Windows
(, last modified 23-Oct-2015, size 822K)

Just unzip the file and put the .exe file somewhere convenient (it does not take up a lot of space, so fits nicely on your desktop). And, just to be clear, the program is completely free. However, we do ask that you do not redistribute it, but refer people to this page instead. That way they will get the latest version and we can keep track of demand.

Do get in touch if you have any comments or questions.

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