How far can you run 1 AWG wire?

At 20 A on a 120 V single-phase circuit, 1 AWG copper stays under 3% voltage drop for about 583 ft one-way. At 240 V the same load reaches roughly 1167 ft, because allowable drop scales with system voltage.

What is the voltage drop of 1 AWG wire per 100 feet?

About 0.62 V at 20 A on 120 V single phase, using VD = 2 × K × I × L / cmil with K = 12.9 for copper.

Is 3% voltage drop a code requirement?

It is a recommendation, not a mandatory limit, in most adopted codes: roughly 3% on the branch circuit and 5% total including the feeder. Some local amendments and specifications do make it enforceable, so check what applies to your job.

Does aluminium change the 1 AWG numbers?

Yes. Aluminium uses K = 21.2 instead of 12.9, so drop is about 64% higher for the same size and run, and allowable distance falls by roughly the same proportion.

1 AWG Voltage Drop — Max Run Length by Load

Voltage drop for 1 AWG copper and aluminium: at 20 A on 120 V single phase the 3% limit is reached at about 583 ft one-way. Full table by load, voltage and distance.

Quick answer

1 AWG copper reaches 3% voltage drop at about 583 ft one-way carrying 20 A on a 120 V single-phase circuit. At 100 ft the same load drops 0.62 V (0.51%), calculated as VD = 2 × K × I × L / cmil with K = 12.9 for copper and 83,693 circular mils.

3% limit @ 20 A, 120 V

583ft

3% limit @ 20 A, 240 V

1167ft

Drop @ 100 ft, 20 A

0.62V

Ω / 1000 ft (Cu)

0.1239

Maximum one-way run length at 3% drop

Copper 1 AWG. Aluminium distances are roughly 62% of these figures.

Load	120 V 1Ø	240 V 1Ø	208 V 3Ø	480 V 3Ø
5 A	2,335 ft	4,671 ft	4,674 ft	10,788 ft
10 A	1,167 ft	2,335 ft	2,337 ft	5,394 ft
15 A	778 ft	1,557 ft	1,558 ft	3,596 ft
20 A	583 ft	1,167 ft	1,168 ft	2,697 ft
25 A	467 ft	934 ft	934 ft	2,157 ft
30 A	389 ft	778 ft	779 ft	1,798 ft
40 A	291 ft	583 ft	584 ft	1,348 ft
50 A	233 ft	467 ft	467 ft	1,078 ft
60 A	194 ft	389 ft	389 ft	899 ft
80 A	145 ft	291 ft	292 ft	674 ft
100 A	116 ft	233 ft	233 ft	539 ft

Source & method: Derived from VD = 2 × K × I × L / cmil (1.732 × K × I × L / cmil for three phase), solved for L at 3% of nominal voltage. Run your exact circuit.

Voltage drop by distance at common loads

Distance	10 A	15 A	20 A	30 A
25 ft	0.06%	0.1%	0.13%	0.19%
50 ft	0.13%	0.19%	0.26%	0.39%
75 ft	0.19%	0.29%	0.39%	0.58%
100 ft	0.26%	0.39%	0.51%	0.77%
150 ft	0.39%	0.58%	0.77%	1.16%
200 ft	0.51%	0.77%	1.03%	1.54%
300 ft	0.77%	1.16%	1.54%	2.31%

Percent drop, 120 V single phase, copper.

Published standard

Frequently asked

How far can you run 1 AWG wire?: At 20 A on a 120 V single-phase circuit, 1 AWG copper stays under 3% voltage drop for about 583 ft one-way. At 240 V the same load reaches roughly 1167 ft, because allowable drop scales with system voltage.
What is the voltage drop of 1 AWG wire per 100 feet?: About 0.62 V at 20 A on 120 V single phase, using VD = 2 × K × I × L / cmil with K = 12.9 for copper.
Is 3% voltage drop a code requirement?: It is a recommendation, not a mandatory limit, in most adopted codes: roughly 3% on the branch circuit and 5% total including the feeder. Some local amendments and specifications do make it enforceable, so check what applies to your job.
Does aluminium change the 1 AWG numbers?: Yes. Aluminium uses K = 21.2 instead of 12.9, so drop is about 64% higher for the same size and run, and allowable distance falls by roughly the same proportion.

1 AWG Voltage Drop — Max Run Length by Load

Maximum one-way run length at 3% drop

Voltage drop by distance at common loads

Frequently asked

More on 1 AWG

Related charts & calculators