Guide
How to estimate conduit for low-voltage jobs
Short answer: measure every conduit run along its real route, add the rises and drops, pick the trade size from the cables it must carry (about 40 % fill for three or more cables), keep pull points within two 90° bends and 100 ft, and price it per foot with your labour.
1. Measure the route
- Along the route – corridors, around beams and ducts – not the straight line.
- Rises and drops – up from the box, down to the device, stub-ups into the ceiling.
- Waste and offsets – usually 5–10 % on top.
2. Choose the trade size (fill)
A common rule (NEC Chapter 9, Table 1, used as good practice for low-voltage too): one cable up to 53 % of the inside area, two cables 31 %, three or more 40 %. With a Cat6 cable about 0.25 in thick, roughly:
| EMT trade size | Inside area | About how many Cat6 (40 %) |
|---|---|---|
| 3/4″ | 0.53 in² | 4 |
| 1″ | 0.86 in² | 7 |
| 1-1/4″ | 1.50 in² | 12 |
| 1-1/2″ | 2.04 in² | 16 |
| 2″ | 3.36 in² | 27 |
Check the outside diameter on your cable’s data sheet – Cat6A and shielded cable are thicker. Leave room for future cables.
3. Bends and pull points
The cabling standard ANSI/TIA-569 asks for no more than two 90° bends and no more than 100 ft (30 m) between pull points – put a pull box where a run needs more. Use long-radius bends for fibre and Cat6A.
4. Walls, floors and fire
Count a sleeve for every wall and floor the cables cross, and firestop every penetration of a fire-rated wall or floor with a listed system. Note the rating (e.g. 1 hr, 2 hr) on the plan.
5. Price it
- Material per foot for each type and size (EMT, PVC, flex…) – couplings, connectors and straps included, or as extra lines.
- Labour per 100 ft – your own rates, higher for rigid, high ceilings and exterior work.
- Fittings and boxes: pull boxes, LBs, stub-ups, sleeves, access panels.
Questions
Does low-voltage cable need conduit?
Not always – plenum-rated cable on J-hooks is common above ceilings. Conduit is used where cable is exposed, outdoors, in walls you cannot fish, or where the specification asks for it.
How does GITECHY Design help?
Draw the conduit or set each cable’s pathway; it measures every type and trade size and prices it per foot with labour in the parts list.
Related
Let GITECHY Design do the math
Cable lengths, PoE and power budgets, batteries, voltage drop and camera coverage – on every design. One flat price per company.