AWG stands for American Wire Gauge. Lower numbers mean thicker wire. A 10 AWG cord handles more current than a 16 AWG cord. Extension cords are most commonly 16, 14, 12, or 10 AWG.

Why does cord length affect the gauge I need?

Longer cords have more resistance, which causes a larger voltage drop at the outlet end. To keep voltage drop below 5%, you need thicker wire for longer runs.

Can I use a 16 AWG cord for a 15-amp circuit?

Only for short cords under 25 feet at light loads. For 15 A loads beyond 25 feet, step up to 14 AWG or 12 AWG to stay within safe voltage drop limits.

What is the maximum length for a 12 AWG extension cord?

At 15 A on 120 V, a 12 AWG cord keeps voltage drop under 5% up to roughly 100 feet. Beyond that, use 10 AWG or run a permanent circuit.

Does this tool apply to outdoor extension cords?

Yes — gauge requirements are the same outdoors. Make sure the cord is also rated for outdoor use (look for "W" in the jacket marking, e.g. SJTW).

What voltage drop percentage is acceptable?

The NEC recommends no more than 5% voltage drop for branch circuits and feeders combined. Most extension cord charts target 3–5%. Motor loads are especially sensitive to low voltage.

Extension Cord Gauge Selector

Name: Extension Cord Gauge Selector
Availability: InStock
Author: Nham Vu

Enter your load amps and cord length to get the safe AWG gauge for your extension cord.

Cord Parameters

Voltage

Load (amps) — total draw of all devices on this cord

Tip: check the nameplate on your device for amps or watts ÷ volts.

Cord length (feet)

Enter your parameters and click Calculate.

Common Extension Cord Gauge Reference (120 V, ≤5% voltage drop)

AWG	Max amps	Up to 25 ft	Up to 50 ft	Up to 100 ft	Up to 150 ft
16 AWG	13 A	OK	OK (<10 A)	Oversize needed	Oversize needed
14 AWG	15 A	OK	OK	OK (<13 A)	Oversize needed
12 AWG	20 A	OK	OK	OK	OK (<15 A)
10 AWG	30 A	OK	OK	OK	OK

Summary