Keystroke Level Model Calculator

Type a sequence of keystroke-level operators, such as MHPKPK, and the calculator adds up the time an expert user would take.

Operators K, P, H, M and R, in upper or lower case. Anything else is ignored.

Response time for each R, in seconds R is the time the system takes to respond, which you measure for your own system.

Total: 4.35 seconds for 6 operators

Breakdown

Operator	Count	Time each	Subtotal

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 of (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.

For example, getting to the Insert, Break dialog in Microsoft Windows while in the middle of typing looks like this in KLM terms:

MHPKPK

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: 1.35 + 0.4 + 2 × (1.1 + 0.2) = 4.35 seconds.

KlmCalc for Windows

The original Windows version of the calculator does the same sum. Type a string of operators and the result appears; the Clear button starts again.

Download KlmCalc V1.0 for Windows (zip file). Unzip it and put the .exe file somewhere convenient. It is free, but please link to this page rather than passing the file on, so people always get the latest version.

Comments and questions are welcome through the contact form.