Outdoor cord voltage drop
Companion estimate for 120V holiday light loads on an outdoor extension cord — AWG, length, and amps to approximate voltage drop (not a full feeder design).
Formula
V_drop ≈ 2 × length_ft × amps × R_ohm_per_1000ft ÷ 1000 · % = V_drop ÷ 120 × 100
Thicker wire = lower AWG number = less drop.
Estimate only — not electrical advice or code compliance. Use outdoor-rated cords, respect amp ratings, and do not daisy-chain long thin cords under heavy loads.
FAQ
What percent drop is concerning?
Many lighting guides aim to stay near or under about 3–5% on 120V. Large drops can dim bulbs at the far end.
Why multiply length by 2?
Current travels out and back, so one-way feet are doubled in this simple copper resistance model.
Is this for whole-house feeders?
No — it is a holiday-display companion for extension cords and light loads, not panel or feeder sizing.
How do I get amps?
Amps ≈ watts ÷ volts. You can also cross-check with the outlet load calculator.