Cable Run & BOM Planner.

Most signal and power cables are made up in standard stock lengths so they coil and pack tidily, typically around 3, 5, 10, 15, 20, 30 and 50 metres. When you plan a run you round the measured distance up to the next stock length rather than buying an exact custom length, which is why a 22 m run is packed as a 30 m cable. This calculator does that rounding for you and totals the cables by type into a bill of materials.

Add roughly 10 to 15 percent on top of your measured distances to cover service loops at each end, dressing cable along trim and skirting, and routes that have to go around obstacles instead of straight across. It is also good practice to carry a couple of spare cables of each common type in case one fails on the day. Tape-measured straight-line distances almost always come up short once the cable is actually run.

XLR carries balanced line-level and mic-level audio signal and is used for microphones and connecting between mixers, amps and active speakers. Speakon carries high-current amplified speaker-level output from an amp to a passive loudspeaker, so it uses heavier conductors and a locking connector. DMX is a control data cable for lighting and is electrically different from audio cable, so even though a DMX lead looks like an XLR lead you should not mix them up, as audio cable used for DMX can cause data errors on longer runs.

As a rough teaching guide, balanced analogue audio is usually reliable to around 100 metres, and DMX lighting control is generally considered safe to about 300 metres before you need a splitter or repeater. A standard Cat network run is normally kept under about 100 metres before you need a repeater or fibre, while HDMI starts to struggle past roughly 10 to 15 metres on passive copper and needs an active cable, extender or SDI conversion for longer pulls. Power cable is the opposite concern: the longer the run and the higher the current, the more voltage drop you get, so heavier conductors are used for long power feeds.

Working out a cable bill of materials in advance tells you exactly how many of each type and length to pack, so you do not arrive on site three Speakons short or with everything too short to reach the stage. It also keeps the rig tidy because each run is matched to a sensible stock length rather than a 50 m cable coiled up to cover a 6 m gap. A clear list speeds up the pack, the bump-in and the bump-out, and makes it obvious what needs to come back.