Electrical takeoffs are counted differently than most other trades — instead of a continuous linear or square-footage measurement, the core unit is the individual device (outlet, switch, fixture box) read off the plan's electrical schedule or symbol legend.
Device count
Device count comes directly from the plan's electrical layout — outlets, switches, light fixtures, and any dedicated circuits (appliances, HVAC equipment) each get counted and categorized by circuit type, since that determines wire gauge and breaker sizing downstream.
Wire runs
Wire runs are estimated by tracing an approximate path from each device back to the panel location, typically using a rule-of-thumb multiplier (often 1.5–2x the straight-line distance) to account for routing through walls, around framing, and up/down between floors rather than a direct line — a straight-line distance alone reliably under-orders wire.
Panel sizing
Panel sizing depends on total connected load across all circuits plus code-required safety margins — this is a load calculation governed by electrical code, not a simple device count, and should be confirmed against the applicable code (often the NEC in the U.S., with local jurisdiction amendments) rather than estimated by rule of thumb alone.
Do not miss dedicated circuits
Where estimators most often miss: dedicated circuits for large appliances (ranges, dryers, HVAC) each need their own wire run and breaker space accounted for separately — lumping them into a general device count understates both wire footage and panel capacity needed.