Estimating an Electrical Bill of Materials from a Circuit Schedule

The circuit schedule tells you what protects each load. The BOM tells you what to buy. Bridging the two is disciplined quantity takeoff.

Conductor lengths

For each circuit: measure the homerun from the panel to the first outlet along the likely routing (not straight-line), add the run between outlets, and add vertical drops.

• Ceiling-height drop to a switch: ~1.2 m each.
• Drop to a convenience outlet: ~0.3 m each.
• Add 10–15% wastage for terminations, offcuts, and pulling slack.

Conduit

Conduit length roughly equals the single-run wire route (not multiplied by conductor count). Add couplings at one per 3 m of EMT, connectors at two per box, and one bushing per connector into a box.

Boxes, fittings, and supports

Devices and equipment

Count directly from the plans: switches, receptacles, cover plates, luminaires, panelboards, breakers (by rating from the schedule), disconnects, and the service equipment. These are usually the largest cost lines.

Assemble and price

Group by category (conductors, raceway, boxes/fittings, wiring devices, luminaires, distribution equipment), apply current unit prices, add labour as a percentage or from a labour-hour table, and total.