Custom Cable Length Calculator

Working Principle

A custom cable is measured along the path it actually travels, not the straight-line distance between the keyboard and the host. The path has three parts. First, the run from the keyboard's port to the edge of the desk, which depends on where the port sits and how far the board is from the desk edge. Second, the drop from the desk edge to the host port, which is roughly desk height minus the port height on the machine. Third, the horizontal offset from the keyboard's position to the host's position across the desk. Summing these gives the working length. Coiled cables complicate this because a coil consumes length that is not available for reach: a coil section is specified by its own length when relaxed, and the usable straight portion is what remains at each end. A common configuration is a 15-20 cm coil section with a straight run at the keyboard side and a longer run to the host. Finally, every cable needs slack. Without it, any keyboard movement pulls on the connector and stresses the port, which is the most common cause of a loose USB-C jack on a keyboard PCB. Ten to fifteen percent slack over the computed path is the practical range, and detachable cables using an aviator connector need extra allowance for the connector body, which typically adds 4-6 cm of rigid, non-bending length.

How to Use

1. 01Measure the distance from your keyboard's port to the nearest desk edge along the route the cable will take.
2. 02Measure desk height and the height of the host port from the floor; the tool computes the drop.
3. 03Enter horizontal offset if the host sits to one side rather than directly below.
4. 04Choose straight or coiled, set the coil length if applicable, then set slack percentage.
5. 05Note: order slightly long rather than short. A cable that is 10 cm too long is tidy with a clip; one that is 5 cm short is unusable.

FAQ

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