How to Do an Electrical Takeoff,
Step by Step

Start with the symbol legend and schedules

Before you count a single device or measure a single run, open the symbol legend and read it. Every design firm uses a slightly different symbol set — what one engineer draws as a duplex receptacle, another draws with an extra hash mark or a subscript letter that changes the circuit type entirely. Skipping the legend means you are guessing at intent rather than reading it, and guesses compound across hundreds of symbols.

The three documents that will serve as your reconciliation targets for the entire takeoff are the panel schedule, the fixture schedule, and the one-line diagram. Pull them before you open the floor plans. Knowing how many circuits Panel A is supposed to carry means you have a hard number to check your homerun count against, not an open-ended tally you close whenever you feel done.

The last thing to verify before any measurement begins is the drawing scale. Large-format drawings reduced to 11×17 or printed at a non-standard zoom throw off every conduit length you calculate. Check the scale bar against a known dimension on the architectural plan — a door is typically 3′ wide, a stairwell bay 10-12′ — and confirm the printed scale matches the title block. A 20% reduction in print size translates to a 20% undercount on conduit footage across the entire job.

Count devices cleanly

The cardinal rule of device counting is one type per pass. Pick one symbol — say, standard duplex receptacles — and work through every electrical plan sheet marking each one as you go. Do not try to count receptacles and switches and fixture types on the same pass. The cognitive load of tracking multiple symbols at once is where double-counts and miss-counts both come from.

Common symbols to know cold: a duplex receptacle is a circle with two short parallel lines perpendicular to the wall; a single-pole switch is the letter S; a three-way switch is S3; a smoke detector is SD; lettered fixture types (A, B, C and so on) correspond to rows in the fixture schedule. GFCI receptacles, weather-resistant receptacles, and hospital-grade outlets share the base symbol but carry a modifier — G, WR, and HG respectively in most sets. These modifiers matter because unit material cost differs meaningfully across grades, and the NEC requires specific grades in bathrooms, kitchens, garages, and exterior locations.

Once a type is fully counted and marked, transfer the total to your takeoff sheet immediately and note the sheet numbers you covered. If the job has 14 electrical sheets and you only counted 12 before being interrupted, you will know where you stopped rather than re-counting sheets you already covered. Reconcile your device totals against the fixture schedule line items before moving to conduit — a mismatch of more than 2-3% is worth tracing rather than ignoring.

Measure conduit, then derive wire

Conduit quantity drives wire quantity, so run them in that order. For each circuit, measure the horizontal run length from device to panel homerun, then add vertical drops and risers — the distance from the ceiling plane down to device height (typically 18 in above finish floor for a standard outlet, 48 in for a switch) and the distance from the ceiling up to the panel feed point. On a 10-ft finished ceiling, each outlet adds roughly 8.5 ft of vertical conduit that the plan view does not show.

Once conduit footage is measured, derive wire footage by multiplying by the number of conductors in the circuit and adding termination allowances. The standard rule of thumb from Universe Estimating (2025) is 2-3 ft at each panel for the panel-end termination loop and 6-12 in at each device for the device-end pigtail. A 15-circuit home-run conduit that is 60 ft long with 3 conductors works out to roughly 60 × 3 = 180 ft of conductor plus 3 ft at the panel and 0.75 ft per device, assuming 15 devices on that homerun. That termination allowance is easy to forget and it adds up to 20-40 ft on a single run.

Break wire into separate line items by AWG size and insulation type. Typical breakdown for commercial work: #12 THHN for 20A branch circuits, #10 THHN for 30A circuits and some HVAC feeds, #8 and larger THHN or XHHW for sub-feeds and feeders. Residential NM (Romex) is its own line item — 12/2, 12/3, 14/2, and so on — because it prices differently from individual THHN and is ordered by the roll rather than by the pound.

Reconcile against the panel schedule

When conduit and wire footage is complete, go back to the panel schedule and match your homerun count circuit by circuit. Every circuit on the schedule should correspond to a homerun on the floor plan. A circuit slot that appears on the schedule but has no identifiable homerun on the drawing is an RFI — not an assumption you make at bid time. Price the takeoff as drawn and note the open item in your bid clarification letter so the GC and owner know there is a question outstanding.

The one-line diagram is the authority for feeder sizes, not the floor plan. Floor plans sometimes omit feeder conduit or show it schematically; the one-line lists the actual conductor sizes, conduit type, and overcurrent protection for every feeder run. Pull feeder quantities from the one-line and price them separately from branch circuit wire. A 4/0 aluminum feeder running 200 ft to a sub-panel is a significant line item and deserves its own row in the estimate rather than disappearing into a wire summary total.

Lighting control systems — occupancy sensors, dimmer panels, low-voltage switching — often appear on a separate Controls drawing sheet. Confirm whether that sheet is in scope. Low-voltage control wiring is typically Class 2 wiring under NEC Article 725 and prices at a different labor and material rate than power wiring. If it is in scope, count it separately and apply the correct labor unit.

Apply waste and price

Wire waste is unavoidable. Rolls end with a remnant, conduit bends consume length beyond the straight measurement, and field conditions add runs not shown on the plan. Standard practice is to add 5-10% wire waste on top of the calculated footage, then round up to the nearest standard reel size. A 600-ft THHN calculation rounds up to a 1,000-ft spool, not a partial spool purchased at a premium and stored with a cut end degrading.

Copper conductor pricing is volatile and should be pulled close to the bid date, not from last quarter. Conductor prices rose 14-17% in early 2025 (Universe Estimating / Breaking AC, 2025), driven by tightening copper supply against data-center and renewable energy demand. An estimate priced off six-month-old wire pricing on a job that bids in 90 days carries real commodity risk. Some estimators add a copper escalation allowance as a separate line item on larger jobs; at minimum, price wire within two weeks of submission.

Use the per-square-foot benchmarks from Universe Estimating and Breaking AC (2025) as a cross-check on your detailed estimate, not as the estimate itself. If a 3,200-sf residential job priced out at $1.10/sf rough-in, something was missed. If it priced at $6.50/sf rough-in, either the home has exceptional complexity or there is a takeoff error inflating a number somewhere. The sanity check catches gross misses before the number goes out the door.

Frequently asked questions

What’s the first step of an electrical takeoff?

Read the symbol legend and verify the drawing scale. A reduced or mis-scaled print corrupts every conduit measurement that follows. The legend ensures you are reading each symbol correctly before any counting starts.

How do I count devices without errors?

Count one device type per sheet, mark each symbol as you go, and reconcile totals against the fixture and panel schedules. Tracking multiple symbol types in a single pass is the primary source of both double-counts and miss-counts on larger plan sets.

How do I turn conduit footage into wire footage?

Multiply conduit footage by the number of conductors per circuit, then add 2-3 ft at each panel and 6-12 in at each device for terminations. Break the result into line items by AWG size and insulation type before pricing.

How do I verify my electrical takeoff?

Match your homerun count to the panel schedule circuit count and confirm feeder sizes against the one-line diagram. Discrepancies become RFIs that belong in your bid clarification letter, not assumptions baked silently into the number.

What’s a good per-square-foot sanity check?

Residential electrical rough-in runs about $2-$4/sf and full install $4-$9/sf, useful for cross-checking a detailed takeoff. These benchmarks catch gross errors; they are not a substitute for a line-item count.

Does AI speed up an electrical takeoff?

AI can auto-count repetitive device symbols and trace runs on vector PDFs, cutting the counting phase significantly. You still reconcile against the schedules before bidding — AI handles the mechanical counting; the estimator handles the judgment calls on scope, RFIs, and pricing.