TradesHow this works
A cabling job has two takeoffs. The first is how much cable to buy: every drop is its run plus slack for the service loops, and cable comes in 1000 ft boxes, so the count rounds up. The second is the raceway: a conduit can only be packed so full before a pull risks damaging the cable.
This does both. It totals the cable and turns it into boxes, then sizes the smallest conduit that holds your bundle at the TIA 40 percent fill and shows the headroom. Switch the cable type and the conduit changes, because a fatter cable like Cat6a fills a raceway faster than Cat6. It also flags a run past the 100 m twisted-pair limit, where the answer is fiber, not a bigger box.
Common questions
How much cable do I need for my drops?
Multiply the number of drops by the average run length, then add a service-loop allowance at each end so you have slack to terminate at the rack and the outlet. The tool does that and rounds up to whole 1000 ft boxes, which builds in a little cushion so you do not come up short mid-pull.
How many network cables fit in a conduit?
The industry guide is the TIA-569 40 percent maximum fill for the first install, which leaves room to pull without stressing the cable. A 1 inch EMT holds about six Cat6, and a bigger cable like Cat6a fills the same conduit faster. The tool sizes the smallest conduit that keeps your bundle under 40 percent and shows how many more would fit.
Why 40 percent and not more?
Comms cable is delicate, and packing a conduit tight drives up pull tension and the chance of kinking or stretching a pair, which shows up later as a failed certification. Forty percent is the recommended starting fill. Bends between pull points eat into that further, so on a run with several elbows, plan for a pull box or an upsize.
Sources: Conduit fill: TIA-569 40% maximum for comms cable · Conduit interior areas: NEC Chapter 9 Table 4 (via necData) (2023) · Cable OD: typical UTP values (manufacturer-dependent). Engine version 1.0.0. Risk tier 1.