Extension cord gauge picker
Suggest a common outdoor extension-cord AWG from load amps and one-way cord length for holiday light runs.
amps = watts ÷ 120 · pick thickest needed AWG so typical length × amp chart stays in a safe outdoor range
When to use
Reach for the extension cord gauge picker calculator when a decorating decision depends on measurements you already have. You will enter total watts on the cord and one-way cord length (feet).
Suggest a common outdoor extension-cord AWG from load amps and one-way cord length for holiday light runs. Compare the panel result to the worked example, then adjust for spare strands, wind, or oddly shaped eaves.
Do not treat the output as an electrical-code stamp, install quote, or substitute for ladder safety and outdoor-rated gear.
Worked example
Start with the calculator’s default entries: Total watts on the cord = 400; One-way cord length (feet) = 50; Supply voltage = 120 V.
With those entries the calculator returns:
Estimated load: 3.33 A
Suggested cord: 16 AWG outdoor-rated (or thicker)
Rule of thumb for ~50 ft at 3.3 A. Always verify the cord's printed rating.
Formula used: amps = watts ÷ 120 · pick thickest needed AWG so typical length × amp chart stays in a safe outdoor range
Recompute the first line by hand from the formula. If your arithmetic and the result differ by more than rounding, the usual cause is a unit mix-up (inches vs feet, percent vs decimal) rather than the formula.
What changes if you change one input? Raise Total watts on the cord from 400 to 600 and leave everything else alone. The result becomes:
Estimated load: 5.00 A
Rule of thumb for ~50 ft at 5.0 A. Always verify the cord's printed rating.
Changing one measured value at a time like this shows which input drives the answer, so you know which value is worth measuring twice before you buy.
Limits / assumptions
This extension cord gauge picker page models only the arithmetic in the formula box. Taste, HOA rules, and neighbor sightlines are still on you.
Recheck against the worked example after any browser or copy change. If your setup violates an assumption on the page, do not lean on the headline number alone.
Output is for estimating and shopping lists — not a legal determination and not a replacement for outdoor electrical safety.
Planning aid only — not electrical advice. Use outdoor-rated cords, respect printed amp ratings, and avoid daisy-chaining thin cords under heavy loads.
FAQ
What does lower AWG mean?
Lower AWG is thicker wire (e.g. 12 is thicker than 16) and usually handles more amps over distance.
Why does length matter?
Longer cords increase voltage drop; heavier loads on long runs need thicker wire.
Indoor vs outdoor?
Use cords marked for outdoor use for yard displays. This picker assumes outdoor holiday lighting.
Want voltage drop numbers?
Open the outdoor cord voltage drop calculator for an approximate % drop.